It has all come down to Game 7 on Tuesday night for the St. Louis Blues and Dallas Stars in the Western Conference semifinals. We debate the key factors that will determine the outcome and make our picks.

Who or what will be the X factor for Game 7 of Stars-Blues, and who ya got?

Greg Wyshynski, senior NHL writer: I'm taking Dallas. I don't want to. I picked the Blues in this series and to emerge from the West, and my postseason prognostications have been so putrid that I really don't need any more red on my ledger. But Ben Bishop is the X factor:

• Bishop is on the road, where he has been great: a .931 save percentage in the regular season, and having given up two or fewer goals in four of six playoff road games.

• Bishop is playing after a loss; he's 3-1 in the postseason following a loss, with a .937 save percentage.

• Bishop is playing in a Game 7, where he's 2-0 with two shutouts.

And couldn't you see the ultimate story here being the collarbone incident in Game 6 followed by a Game 7 win? Plus, the Blues have been weirdly ordinary at home in the playoffs: 2-4, including two losses to Dallas in this series. So I would like to be wrong here, as the Blues are my pick. But it's hard to ignore what the Stars have going for them in Game 7.

Emily Kaplan, national NHL reporter: I'm picking the St. Louis Blues. The X factor that's going to make or break them? Special teams, an area where the Stars have had a clear edge so far. Dallas has been short-handed 20 times in this series for a total of 33:45 -- most of any second-round team -- and has killed off 90 percent of penalties. The Blues looked like they were making some power-play adjustments in Game 6. Despite going 0-for-5, I think they can break through in Game 7. Just as important is stopping the Stars' power play, which has gone 4-for-14 (28.6 percent, also best among second-round teams). Show proficiency in either one of those areas, and I see St. Louis prevailing.

Chris Peters, NHL draft and prospects writer: Seeing as I'm 0-for-the playoffs in predictions, I apologize to Blues fans for picking them in this Game 7. The X factor is Ryan O'Reilly, who has really not seemed to be himself in these playoffs. The big forward was a big reason the team made it to the postseason at all, given his career-high 77 points and solid all-around play since being traded to St. Louis last summer. In this series, O'Reilly has looked mostly fine for stretches, but one wonders if the adrenaline of a Game 7 could cure what ails him, if he is indeed playing through something. With the Blues able to play the matchups a bit more to their favor on home ice in Game 7, the stars are aligning to set up O'Reilly for a big breakout after posting five assists in the series so far.

Dimitri Filipovic, hockey analytics writer: I picked the Stars to win in seven before the series, so I have to stick with that at this point. It's a bit of a cop-out to say that the goaltending will be the deciding factor of a hockey game, but in this particular case it really is warranted because Ben Bishop's play has been the ultimate barometer for the Stars' chances of winning. In the three games they've won in this series, he has stopped 97 of the 102 shots he has faced (.951 save percentage). In the three games they've lost, he has stopped just 63 of the 74 shots the Blues have thrown at him (.851 save percentage). He has been nothing short of outstanding all season for them, fully earning his nomination as a Vezina Trophy finalist. Dallas will go as far as he'll take them, and assuming he's good to go following his injury scare in Game 6, the Stars will need at least one more gem from him in what will surely be a tense, tightly contested elimination game with little margin for error.

Ben Arledge, associate NHL editor: I originally took the Blues in seven, and they are coming off a big win facing elimination. And they are probably the better team on paper. And they are at home. There isn't a whole lot of reasoning for a change at this point, so let's ride with St. Louis. There are two big X factors here. First, Bishop's shoulder. He caught a Colton Parayko rocket off his collarbone in Game 6 and didn't finish the contest. The mere fact that he left the game worries me a bit, as it seems to suggest something more serious than a stinger, but it's equally likely the club was just playing it safe given the three-goal deficit. And while Anton Khudobin has been terrific this season in his own right, the Stars need Bishop at 100 percent to win, for the reasons outlined by Dimitri above. Second, I'd keep an eye on Mats Zuccarello. Despite skating somewhere between two to four minutes less per game than the other offensive catalysts on the Dallas side, the diminutive Norwegian has seven assists in the series. If Dallas is going to win this, he's going play a part, even if it's behind the scenes. He has plenty of playoff experience from his days with the New York Rangers, and knows what it takes to win a Game 7.

Down 3-0 after the first leg at the Camp Nou, Liverpool did the unthinkable at Anfield, turning around the tie with four answered goals in one of the greatest comebacks the Champions League has ever seen.

With a three-goal deficit and without two of their famed front three in Mohamed Salah and Roberto Firmino (both injured), Liverpool got two goals apiece from Divock Origi and Georginio Wijnaldum to shock Lionel Messi and Barcelona and reach the Champions League final.

Here's how social media reacted to the latest -- and maybe most improbable -- in a long line of magical European nights at Anfield...

A MIRACLE IN ANFIELD!

Down 3-0, Liverpool come back to defeat Barcelona and reach the Champions League Final for the second straight year ? pic.twitter.com/Ftx5Xl6f5t

— SportsCenter (@SportsCenter) May 7, 2019

Hard to argue with this quote after watching that performance from Jurgen Klopp's Liverpool and the fans at Anfield.

"Here is one thing everyone inside Anfield knows, including our opponents. This Liverpool never stops. This Liverpool never quits. This Liverpool gives everything at all times." ❤️ pic.twitter.com/0ELb61N8Ab

— Liverpool FC (@LFC) May 7, 2019

Mo Salah believed.

We never do, Mo! ?#AllezAllezAllez pic.twitter.com/B0oTiXWRc7

— Liverpool FC (@LFC) May 7, 2019

Count investor Lebron James in among those who were captivated by Liverpool's comeback.

??‼️‼️‼️‼️‼️‼️ AMAZING NIGHT FOR THE REDS. WOW‼️‼️ #YNWA❤️ https://t.co/n9tuwtaj8z

— LeBron James (@KingJames) May 7, 2019

BT Sport brings up a good point: Where does this comeback rank among Liverpool's greatest?

2005: Liverpool 3-3 AC Milan

2016: Liverpool 4-3 Dortmund

2019: Liverpool 4-0 Barcelona

This. Club. Does. Comebacks. pic.twitter.com/y52v9Hh8Tz

— Football on BT Sport (@btsportfootball) May 7, 2019

Seven percent chance of advancing... tell that to Liverpool!

How unlikely was Liverpool's comeback?

- Barcelona was -3000 to reach the final, according to Westgate

- FiveThirtyEight's Soccer Power Index gave Liverpool a 7% chance to advance

- They didn't have their 1st and 3rd-leading scorers from the last 2 years (Salah & Firmino). pic.twitter.com/qHD3IjY1Mm

— ESPN Stats & Info (@ESPNStatsInfo) May 7, 2019

Let's check in with some of the heroes from the night...

Liverpool produced one of the greatest comebacks in Champions League history to beat Barcelona 4-0 on Tuesday, overturning a three-goal first-leg deficit and advancing to their second successive final with a 4-3 aggregate victory.

Two goals each from stand-in forward Divock Origi and halftime substitute Georginio Wijnaldum left Lionel Messi and Barcelona utterly shell-shocked by a Liverpool performance full of passion, belief and determination.

Juergen Klopp's side will play the winner of Wednesday's other semi-final between Ajax Amsterdam and Tottenham Hotspur, with the Dutch side leading 1-0 from the first-leg in London.

"Unbelievable. I don't think many people gave us a chance," said Liverpool captain Jordan Henderson.

"Before the game we knew that it would be difficult but it was still possible of course. It's amazing. We knew that at Anfield we could do something special."

Liverpool become only the third team in the history of the European Cup or Champions League to come from three goals down after the first leg of a semi-final and progress after Panathinaikos in 1970-71 and Barcelona themselves in 1985-86.

For Barca, who went out to on away goals to AS Roma in the quarter-finals last year after winning the first-leg 4-1, it was a bitter night that will raise many questions for coach Ernesto Valverde.

Messi, whose two goals in the first leg had given his team a seemingly comfortable advantage, was unable to make his influence on the game count with an away goal that would have been decisive.

Liverpool, without two thirds of their strike force with Mohamed Salah and Roberto Firmino injured, took a seventh-minute lead when a poor headed clearance from Jordi Alba fell at the feet of Jordan Henderson, who burst goalwards.

His low shot was parried out by Barca keeper Marc-Andre ter Stegen but straight to Origi who slotted home.

Barca had openings in the first half but when Messi twice got space around the box he fired wide of the target and when Jordi Alba burst goalwards just before halftime, Liverpool keeper Alisson Becker was out quickly to nullify the danger.

Yet the game took a remarkable turn following the introduction of Liverpool midfielder Georginio Wijnaldum for the injured left back Andy Robertson, at the break.

The Dutchman drove home a low cross from Trent Alexander-Arnold, which Barca keeper Ter Stegen should have saved, to make it 2-0 in the 54th minute.

Two minutes later Wijnaldum rose to meet a Xherdan Shaqiri cross with a powerful header to make it 3-3 on aggregate.

Liverpool then grabbed an extraordinary fourth goal with a quickly-taken corner from Alexander-Arnold, catching the Barca defence asleep with a low ball that was turned in at the near post by Origi.

That sent Anfield wild but then Klopp's side suddenly found themselves needing to switch mindset and defend a lead as Barca slipped, belatedly, into their trademark possession game.

Yet with Virgil Van Dijk and Joel Matip outstanding in the centre of defence and Brazilian Fabinho making some crucial interventions in midfield, Liverpool held on for one of their most famous wins.

Klopp's side, who lost to Real Madrid in last year's final in Kiev, remain in with a chance of a double triumph as they head into Sunday's final round of Premier League games trailing leaders Manchester City by just a point.

Oklahoma City Thunder All-Star Paul George underwent rotator cuff surgery to repair a partially torn tendon in his right shoulder Tuesday and will miss at least the start of preseason training camp, league sources told ESPN.

Along with George -- who will also soon have a procedure done to correct a small tear in the labrum of his left shoulder -- All-Star guard Russell Westbrook had a procedure done to repair a torn ligament in a finger on his left hand, league sources said.

Before the injury in late February, George had been considered an MVP front-runner and a Defensive Player of the Year candidate. He is expected to make a full recovery, although it won't be until the preseason when the Thunder next address a time frame for his return.

Westbrook played the final six weeks of the season with the injury to the fourth metacarpal of his non-shooting hand, sources said. Westbrook had been taping and treating the finger throughout the final weeks of the regular season and playoffs but never disclosed the injury to the public.

He also had a minor procedure on his surgically repaired right knee Tuesday -- described as proactive maintenance -- that will allow him time to still have an aggressive summer of preparation for next season, sources said.

George and Westbrook played with the injuries in the final weeks of the Thunder's season, when a promising 3-seed in the Western Conference playoff race culminated with them finishing sixth and losing in the first round to the Portland Trail Blazers.

George injured his right shoulder against the Denver Nuggets on Feb. 26, though he suggested at the team's exit interviews two weeks ago that he had been dealing earlier with a shoulder issue.

George missed three games, returning after a week only to then hurt his left shoulder, though he didn't miss any time because of it. Surgery on his right shoulder was an option at that time, but without a risk of further damage or injury, George elected to play through it and address it after the season. He received regular treatment, including the use of a massive heating wrap while he sat on the bench during games.

His shoulder issues certainly played a part in the way the Thunder's season derailed the way it did. On the morning of Feb. 26, the Thunder were 38-21, third in the Western Conference, and George was a leading candidate for MVP. Prior to the injury, he was averaging 28.7 points per game on 45.1 percent shooting, including 40.3 percent from 3 on 9.6 attempts, self-admittedly playing the best basketball of his career.

After the injury, the Thunder went 11-12 with George playing far more inconsistent, averaging 26.1 points per game on 39.7 percent shooting, including 33.8 percent from 3 on 10.4 attempts.

"I think it came at a terrible time, especially [because] the team was rolling," George said in his season-ending news conference. "We were playing good. I was holding up pretty, pretty, pretty good. I just thought it came at the wrong time, honestly. But again, I've never made no excuses on it. I was dealing with it for a long time throughout the season. It just got worse and worse as it went on.

"... Injuries are part of the game," he added. "I've missed a season being hurt, so I was able to -- the training staff assured me I was fine to play through it, and I will be fine going forward. I'd had no other thought in my mind but to be out there and play and ride it out with my guys."

George aggravated his right shoulder right before the postseason. In the second-to-last game of the regular season, George was skying for a baseline dunk against the Houston Rockets but had his right arm grabbed on the way up. He stayed in and eventually hit a game-winning 3 with a couple seconds left. Unable to lift his arm the next day, George sat out the regular-season finale against the Milwaukee Bucks.

Before Game 1 against the Blazers, George went four days without shooting a basketball and was said to not be able to lift his right arm until the day of the game. He played through the injury in the series, getting routine treatment and adding black KT tape on both shoulders during games. He averaged 28.6 points on 43.6 percent shooting, including 31.9 percent from 3, for the series but closed out strong with 36 points on 14-of-20 shooting.

Westbrook's knee issues originated in 2013 when Patrick Beverley ran into him during the first round of the playoffs. Westbrook suffered a torn meniscus and underwent surgery for a full repair. He went almost five years without any surgeries on his knee before having another scope in September, which caused him to miss all of training camp and the first two games of the regular season.

He averaged a triple-double for the third consecutive season (22.9 points, 11.1 rebounds and a league-leading 10.7 assists). Westbrook averaged nearly two steals per game -- which was fourth in the NBA -- while pairing with George to lead the Thunder into becoming one of the league's best defensive teams during the regular season.

The Washington Nationals reinstated third baseman Anthony Rendon from the 10-day injured list and recalled right-handed pitcher Erick Fedde from Double-A Harrisburg on Tuesday.

Rendon missed a total of 14 games with a left elbow contusion suffered when he was hit by a pitch on April 20. Prior to suffering the injury, Rendon was in the midst of a 17-game hitting streak.

The Nationals also optioned infielder Carter Kieboom to Triple-A Fresno and placed left-handed pitcher Tony Sipp on the 10-day injured list with a strained oblique.

CLEVELAND -- Indians ace Corey Kluber is hopeful he will be able to come back from a broken right arm and pitch again this season.

The two-time American League Cy Young Award winner spoke Tuesday for the first time since he was struck by a 102 mph line drive off the bat of Brian Anderson during a start last week in Miami.

His arm wrapped in a soft cast, Kluber said it has been difficult to stay positive and patient with an injury that has dramatically impacted his season.

Kluber will undergo weekly X-rays so doctors can see if his bone is healing properly.

"I don't have a plan not to pitch again," Kluber said when asked if he thought he could return later this season. "Obviously, I don't have a definitive timeline because it's all depending on how things heal. But in my mind, I'm not looking at it as season ending."

The 33-year-old said it's been challenging to sit around and "be at your body's mercy."

The Los Angeles Angels announced that Shohei Ohtani will make his season debut on Tuesday night in Detroit, batting third against the Tigers.

He will be returning just seven months after undergoing Tommy John surgery.

Ohtani, the reigning American League Rookie of the Year after finishing 2018 with a .925 OPS and a 3.31 ERA, will boost a lineup that is desperate for production behind Mike Trout, who leads the majors with 31 walks.

The 24-year-old Ohtani, who will help only as a designated hitter this season, said last week that his timing was "getting better each day" and that he was "a little ahead of schedule" with his rehab.

The Angels also reinstated third baseman Zack Cozart (neck strain) and reliever Cody Allen (back) from the injured list on Tuesday.

Cozart was placed on the IL last month. He is hitting just .109 with four RBIs this season.

Allen is 0-2 with four saves and a 6.00 ERA this season, his first with the Angels.

He will not return immediately to the closer's role, manager Brad Ausmus said recently. Allen had been removed from the closer's role just days before he was placed on the injured list with a back injury last month.

In other moves Tuesday, the Angels designated outfielder Peter Bourjos and right-hander Chris Stratton for assignment and optioned infielder Luis Rengifo to Triple-A Salt Lake.

British number one Kyle Edmund lost 6-4 6-3 to Italy's Fabio Fognini in the first round at the Madrid Open.

World number 12 Fognini, 31, took one hour and 30 minutes to secure victory as he broke Edmund's serve four times.

Edmund could not recover after losing serve at 4-4 in the first set, or once he went 3-2 down in the second.

It is the Briton's fourth straight defeat, having lost to American world number 82 Denis Kudla in the first round of the Munich Open last week.

The 24-year-old has also lost to Diego Schwartzman in Monte Carlo and, after a first-round victory over Ugo Humbert, to Jo-Wilfried Tsonga in Marrakech on clay this season.

Number one seed Novak Djokovic, 31, progressed to the third round in Madrid, beating 21-year-old American Taylor Fritz 6-4 6-2.

The Serb is joined by potential quarter-final opponent Marin Cilic, after the Croat recovered from a set down against Germany's Jan-Lennard Struff to win 4-6 6-3 6-4.

Competing in his final tournament before retirement, 37-year-old David Ferrer beat fellow Spaniard Roberto Bautista Agut 6-4 4-6 6-4 to set up a second-round tie against third seed Alexander Zverev.

Stan Wawrinka beat France's Pierre-Hugues Herbert 6-2 6-3 and will face Guido Pella in the second round after the Argentine overcame 12th seed Daniil Medvedev 6-2 1-6 6-3.

Meanwhile, Britain's Jamie Murray and partner Bruno Soares reached the men's doubles second round, taking just 18 minutes to win the first set in a 6-0 6-4 victory against Nikoloz Basilashvili and Radu Albot.

Later on Tuesday, Roger Federer will contest his first clay-court match in three years against France's Richard Gasquet, and Barcelona Open champion Dominic Thiem faces Reilly Opeka.

Nadal 'hopes to be ready' despite illness

World number two Rafael Nadal is preparing to begin his tournament with a second-round match against Canada's Felix Auger Aliassime.

A five-time champion in Madrid - most recently in 2017 - Nadal has been struggling with a virus as he aims to improve on back-to-back semi-final defeats.

The Spaniard lost to to Dominic Thiem in Barcelona and Fabio Fognini in Monte Carlo as he failed to defend either of his titles in April.

"I've been going through a virus. The positive side is I've been able to train at least an hour-and-a-half [per session]," said 32-year-old Nadal.

He added: "I hope that tomorrow is going to be a bit better. It's true that when you have this virus and stomach viruses, the body's a bit weaker. I'm a bit better than yesterday and yesterday was better than the day before.

"There is a bit more risk of injuries. But of course, this is a very important tournament for me and I hope to be ready. Barcelona was a positive improvement for me. I'm building up my game with more confidence than I had in Monte Carlo. I'm enjoying training and I enjoy playing each day."