Former European Cup winners had mixed fortunes in Champions League qualifying as Ajax Amsterdam and Red Star Belgrade squeezed into the playoff round while Celtic and Porto were eliminated after a dramatic evening on Tuesday.

Ajax, semifinalists last season, came from behind to beat PAOK 3-2 for a 5-4 aggregate win over the Greeks while Red Star knocked out FC Copenhagen on penalties after a bizarre shootout involving 22 spot-kicks.

Krasnodar sprung a major upset with a 3-2 win at Porto to advance on away goals after losing the home leg 1-0 and Romania's Cluj won 4-3 at Celtic to eliminate the Scottish champions 5-4 on aggregate.

Ajax youth academy reject Diego Biseswar fired PAOK ahead with a thumping shot at the Johan Cruyff Arena before Dusan Tadic, having had a penalty saved, equalised with another one before halftime.

PAOK keeper Alexandros Paschalakis pulled off a string of superb saves but was undone by a Nicolas Tagliafico header and another Tadic penalty before Biseswar set up a tense finish with a stoppage-time effort.

Ghanaian forward Richmond Boakye fired Red Star ahead in Copenhagen and Dame N'Doye levelled to force the shootout in which the Danish champions missed two chances to progress before they were dumped out by visiting keeper Milan Borjan.

Borjan kept Red Star afloat with two stops and netted a spot-kick himself before he sent the away fans into raptures when he blocked Jonas Wind's weak effort to send the Serbians through.

Having earned a 1-1 draw in Romania, Celtic rallied from an early deficit to lead 3-2 before a late collapse gifted Cluj two late goals and a 5-4 aggregate win over the 1967 European champions.

Billel Omrani scored for Cluj after they trailed 2-1 and 3-2 and George Tucudean delivered the final blow in stoppage time as Celtic threw men forward.

Porto fell 3-0 behind to Krasnodar in a dire first half for the Portuguese side as Magomed Suleymanov struck twice after Tonny Vilhena had levelled the tie on aggregate.

The hosts, who have won Europe's premier club competition twice, hit back in the second half through Ze Luis and Luis Diaz but the Russian visitors held on at the Dragao stadium.

Dynamo Kiev looked like overturning a 1-0 first-leg deficit against Club Brugge after Vitaliy Buyalskiy netted early on but the Belgian side hit back.

Stoppage-time substitute Lois Openda silenced the home crowd in Kiev barely a minute after coming on, scoring in the 96th minute to secure a 3-3 draw and book Brugge a playoff clash with Austrians LASK.

LASK followed up their 2-1 win at Basel with a 3-1 home victory over the Swiss team, while Dinamo Zagreb thumped Ferencvaros 4-0 away after a 1-1 home draw with the Hungarians.

Rosenborg beat Maribor 3-1 for a 6-2 overall win over the Slovenians, APOEL won 2-0 at Qarabag to overturn a 2-1 home defeat and Olympiakos beat Istanbul Basaksehir 2-0 for a 3-0 aggregate triumph over the Turkish side.

CLEVELAND -- Boston Red Sox lefty Chris Sale has reached 2,000 career strikeouts faster than any other pitcher in history.

Sale, 30, entered Tuesday's game against the Indians with 1,995 strikeouts. He struck out the side in the first and reached the milestone in the third when he fanned rookie Oscar Mercado.

According to information provided by the Red Sox, Sale broke Hall of Famer Pedro Martinez's mark by getting to 2,000 strikeouts in 1,626 innings. Martinez did it in 1,711⅓ innings, Randy Johnson in 1,733⅓ and Max Scherzer in 1,784.

Sale has struggled this season. He entered his 25th start at 6-11 with a 4.41 ERA. Still, he has the best strikeout-to-walk ratio in the majors since 1920.

Sale is in his third season with Boston after spending seven with the Chicago White Sox. He opened 2019 with four straight losses and didn't get his first win until May 3.

The Houston Dynamo fired manager Wilmer Cabrera on Tuesday, naming assistant coach Davy Arnaud as manager on an interim basis for the rest of the season.

The Dynamo started off the 2019 campaign in scintillating fashion, bursting out of the gate with a 6-1-1 record. But results, especially after its contingent of international players returned from playing for their respective countries, disintegrated. Now Cabrera, who just a year ago led the Dynamo to the Lamar Hunt U.S. Open Cup title, finds himself out of a job. He is the fifth MLS manager to lose his job this season joining FC Cincinnati's Alan Koch, Colorado's Anthony Hudson, New England's Brad Friedel and Real Salt Lake's Mike Petke.

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"We'd like to thank Wilmer for all of his hard work and dedication over the course of the last two and a half seasons with the Houston Dynamo, including last year's U.S. Open Cup title. We wish him all the best moving forward," said Dynamo Senior vice president and GM Matt Jordan. "At this time, we as a club believe the team will benefit from a fresh perspective as we enter the final third of our season and make a push to qualify for the playoffs."

Cabrera had a 32-39-22 record in MLS regular-season play with the Dynamo after taking charge prior to the 2017 season. He had previously managed Chivas USA, coaching the Goats for the 2014 campaign before the team was dissolved. He spent five years as manager of the U.S. U-17 national team from 2012-17, as well as one season with the Dynamo's USL affiliate, the Rio Grande Valley FC Toros, in 2016.

Arnaud was in his third season as a Dynamo assistant, having previously served as an assistant with D.C. United. He steps into the managerial role with just nine games left in the regular season. Houston currently sits in ninth place in the Western Conference standings, six points behind in-state rivals FC Dallas for the seventh and final playoff spot.

As a player, Arnaud spent the entirety of his career in MLS, playing for Sporting Kansas City, the Montreal Impact and D.C. United. He was part of the Kansas City side that won the 2004 Lamar Hunt U.S. Open Cup. During his career he made 368 league and playoff appearances, scoring 54 goals and adding 47 assists.

At international level, Arnaud made seven appearances for the U.S., scoring one goal.

The comparisons are inevitable.

In November 2003, 14-year-old Freddy Adu signed his first professional contract with MLS and D.C. United. In the years since, Adu's career has been held up as a cautionary tale of too much too soon, showing how being the face of a league set the stage for a career that never lived up to the hype. Now another 14-year-old is slated to turn pro and is doing so a few months younger than Adu was when he became a professional.

Late last month, Francis Jacobs signed a professional contract with USL Championship side Orange County SC, and it raises the usual questions. What's the rush? And what efforts are being made to make sure that Jacobs stays on track and doesn't end up going down the route of Adu and other talented teenagers before him?

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Much has changed in the U.S. soccer landscape since Adu made his debut with D.C. United during the 2004 season. The Development Academy was formed in 2007, resulting in academies sprouting up all over the U.S. and Canada, not just in MLS. The entire soccer ecosystem in the U.S. and Canada has considerably more experience in bringing along young pros. Alphonso Davies was 15 when he signed with the Vancouver Whitecaps and now finds himself on the books of Bayern Munich. Earlier this year, the Chicago Fire signed a 14-year-old in goalkeeper Gabriel Slonina.

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Orange County has some experience in this area as well. Last year, the club signed a 15-year-old goalkeeper, Aaron Cervantes. After nine league appearances with the club, Cervantes finds himself in the running to be named to the U.S. roster for the FIFA Under-17 World Cup this October. Given that experience, OCSC's President of Soccer Operations & General Manager, Oliver Wyss, is confident that Orange County will provide the right platform for Jacobs to grow.

"We have a very talented player that is now in a professional environment, that is allowed to go and develop," Wyss said of Jacobs. "He's allowed to make mistakes. He's allowed to be a teenager. But clearly there's a very talented player that we feel, in the structure that we've provided for him, will make a significant difference in the USL and beyond."

OCSC didn't arrive at the decision to sign Jacobs lightly. Manager Braeden Cloutier has been watching Jacobs for years and, in conjunction with Wyss and technical director Frans Hoek, the decision was made to invite Jacobs to train with the team in May. To their surprise, he wowed the OCSC staff with his ability on the ball. At 5-foot-11, he had the physical tools to compete.

"When he came into our environment, not only for the coaching staff but the players as well, to gain the respect of a lot of older players, it's not easy," said Cloutier. "For him to keep the ball, keep the ball moving, make the right decisions, don't turn the ball over, it caught all the players' eyes really quick. It caught our eyes too.

"I've known him for a long time, but I think we were all like, 'Wow, he's well ahead of definitely a lot of kids.'"

Jacobs estimated that it took him two weeks to adapt to the speed of play.

"I was pretty nervous, but once the practice started, it was just a regular practice," Jacobs said of his first sessions with the team. "I was pretty excited to get started and play with them. The pace of play is way faster because these guys are pros, and it's a lot of movement off the ball, which is way faster too."

After Jacobs proved himself over the course of a few months, he accepted an offer -- a "standard professional contract," according to Wyss -- from the club. The teenager has had training stints with FC Koln in 2016 and Bayer Leverkusen in 2017 but the chance to stay near his home in Laguna Beach, Calif. carried the day. There are safety nets in place so Jacobs will be able to play for his youth club, Irvine Strikers, should he need more minutes.

"Taking him out of his nest was not the right move at this point," said Jacobs' father, Jeff, an attorney. "What OCSC has offered couldn't be any better. We live very close by. Francis' life will stay intact in terms of friends and normalcy."

It helped that Jacobs' mother, Cindy, has a Ph.D. in education and has been home-schooling Francis for the past year. For the upcoming school year, Jacobs will be training with his team in the mornings and attending classes in the afternoon at a local private school, with extra training and video sessions with Crettenand at the club four days a week.

"I think after he was out there for two weeks and he had adjusted to the movement and the play of the ball with it pinging all over the place, it was as though from my vantage point, 'Wow, this is what he should be doing regularly," Jeff Jacobs said. "But that's my own thought. It was also, 'What does he want?' and it seems like a natural fit."

The entire OCSC staff doesn't want to throw Jacobs into the deep end. OCSC's Under-23 coach, Didier Crettenand, has been assigned to act as Jacobs' "big brother," breaking down video with the player and helping him navigate his first months as a pro. Former U.S. international Michael Orozco has taken it upon himself to give Jacobs advice during training, too.

"When you watch [Orozco] in practice you notice how good he really is," said Jacobs. "He points out little details that not a lot of people would see in a game. It's really helpful. He's a defender too so from a defensive standpoint, he's showing me how to use your body and not your hands."

Cloutier is also mindful of the age difference between Jacobs and his teammates and how that can manifest itself in the locker room and not just on the field.

"Jacobs is still 14 years old, and there are things said and done in locker rooms that a 14-year-old doesn't need to hear," Cloutier said. "So we're protecting him when it comes to that kind of stuff. He has his kit, so he comes to practice already changed. He comes down when we do video sessions with the team. He's only a little bit involved with the locker room [atmosphere]."

You can already sense some conflicting impulses when it comes to deciding when Jacobs should make his professional debut. Wyss said Jacobs is available for selection and could see the field as soon as this weekend against the Las Vegas Lights (Saturday, Aug. 17, 10 p.m. ET, ESPN+).

Cloutier is more hesitant. OCSC is in 14th place in the 18-team Western Conference but three points out of a playoff spot, so he has to think of the bigger picture. He's also mindful of giving Jacobs his debut at the right time. He noted that the defensive side of the ball is where Jacobs has the most room to grow.

"The last thing I want to do is put him in a situation where if this backfires and doesn't go well, then it's like taking two or three steps backwards," Cloutier said. "I just want to make sure we're doing this at the right pace and the right time."

Jacobs, who also holds a British passport thanks to his mother, whose family moved to England from South Africa in the 1980s, is eager to take that next step but like a grizzled veteran, he knows it's not his call.

Wyss said, "It was clear that Jacobs has all the tools, that if developed correctly, he can be a great professional -- not only for us but to go beyond."

Even though Jacobs has surpassed Adu in terms of his long-held age record in American soccer, he's still got a long way to go before he and OCSC can say he's passed the pitfalls that claimed Freddy all those years ago.

MASON, Ohio -- Serena Williams has withdrawn from the Western & Southern Open, citing a lingering back injury.

The 23-time Grand Slam champion retired because of the same injury during Sunday's Rogers Cup final in Toronto against Bianca Andreescu but had been expected to open play in Cincinnati on Tuesday.

She made the announcement shortly before the start of her scheduled first-round match against Zarina Diyas on Tuesday night.

Williams, a two-time winner at the event, will be replaced by lucky loser Jessica Pegula.

"I am so sad to withdraw from the Western & Southern Open as it is truly one of the tournaments I most love to play," she said in a statement provided by the tournament. "I came to Mason on Sunday and have tried everything to be ready to play tonight, and was still hopeful after my practice this morning. But unfortunately my back is still not right and I know I should not take to the court.

"I really want to thank tournament director Andre Silva and the WTA for giving me every chance to play, and I also want to thank all the amazing fans here in the Cincinnati area for their support -- it means so much. I promise I'll do my best to be back here next year."

Williams is next expected to play in New York at the US Open, which begins Aug. 26 and where she is a six-time champion and the 2018 runner-up.

Indianapolis Colts general manager Chris Ballard said quarterback Andrew Luck's calf strain has become a high-ankle issue.

Ballard isn't ready to say what Luck's status will be for the Week 1 game at the Chargers.

"We're 3 and a half weeks away from regular season, so I'm not ready to say (Luck's regular season is in jeopardy)," Ballard told reporters on a confereence call Tuesday night.

Ballard says "most likely" Luck will not play in the preseason.

Team owner Jim Irsay told SiriusXM NFL Radio on Monday that Luck's ongoing absence from Colts training camp was related to a bone issue in his lower left leg.

The quarterback has been ruled out of practices through Thursday, including a pair of joint sessions with the Cleveland Browns that begin Thursday, according to coach Frank Reich. He has been a participant in walk-throughs and has worked with throwing coach Tom House.

Philadelphia Phillies general manager Matt Klentak said Tuesday that no decision has been made on Jake Arrieta's status in the rotation the rest of the season.

Arrieta was scheduled to meet with the Phillies brass this week to talk about whether he should shut it down for the rest of the season or continue to gut it out.

Arrieta has pitched with a bone spur in his right elbow this summer, with sporadic effectiveness. On Sunday in San Francisco, the right-hander had his worst outing of the season: seven hits, a walk and five runs allowed in three innings on just 66 pitches.

At some point, he needs to have arthroscopic surgery.

Over his past 13 starts, Arrieta has a 5.76 ERA, with 84 hits and 25 walks allowed in 65⅔ innings. He has not pitched well, but the Phillies' rotation has been thin, and Arrieta at least offers the hope of some decent starts.

The Phillies are 60-58 and two games out in the NL wild-card race. If Arrieta's spur treatment and rehab are typical, he could have the procedure at the end of the season and still have time to be ready for the start of next season.

But if he has the surgery now, he would have more time to prepare for 2020 -- a year that might serve as a platform for his next round of free agency.

Kyle Edmund lost to Daniil Medvedev for the second time in six days as the British number one was knocked out of the Cincinnati Masters.

Edmund, 24, suffered a 6-2 7-5 loss on Tuesday after a straight-set defeat at last week's Rogers Cup in Montreal.

World number 30 Edmund, who had won their two matches before last week, led the Russian 5-3 in the second set.

World number eight Medvedev, 23, will now face Benoit Paire of France in the second round.