We're down to the final four in the FA Cup with both matches taking place at Wembley this weekend. First up on Saturday it's Thomas Tuchel's Chelsea up against quadruple-chasing Manchester City. Then on Sunday, 4,000 fans will be in attendance to see Leicester City take on Southampton.

ESPN breaks down everything you need to know ahead of this week's semifinals, including where the games will be won or lost, the key players, and predictions as to who will go through.

Chelsea vs. Manchester City (Saturday, 12:30pm ET on ESPN+)

Overview: Chelsea's fourth-round win over Luton Town in the snow in January proved to be Frank Lampard's final game in charge. He was sacked two days later and replaced by ex-Paris Saint-Germain boss Tuchel, who has made a remarkable start to his tenure in charge of Chelsea. He's lost just one game -- a bizarre 5-2 defeat to West Bromwich Albion at Stamford Bridge -- and has moulded a team that is defensively stable, and anchored on causing as much claustrophobia as possible for the opposition. The Blues are still chasing a top-four spot in the Premier League and are in the semifinals of the Champions League, having edged through 2-1 on aggregate against FC Porto.

Tuchel is yet to face City as Chelsea boss but he knows Pep Guardiola well. He faced him as Mainz and then Borussia Dortmund boss during Guardiola's time in charge of Bayern Munich and the two have kept in touch. Speaking in early March, Tuchel said he learnt "everything about [football]" from Guardiola's Barcelona side and said he has been a "big influence" on his philosophy. But there will be little room for sentiment on Saturday when the two meet.

City are still in the mix for a remarkable quadruple after their 4-2 aggregate win over Dortmund in the Champions League quarterfinals. They have the Carabao Cup final to come on April 25 and are 11 points clear at the top of the league, but Guardiola will want to get his hands on the FA Cup again having won it just once since he took charge of City in 2016.

Chelsea booked their place in the semifinals thanks to a 2-0 win over Sheffield United while Manchester City defeated Everton 2-0 at Goodison Park to keep their dreams of a clean sweep alive.

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Where Chelsea will win or lose: Chelsea will be well structured, and will look to control possession. But that crushing defeat to WBA showed that despite being set up well, they can still capitulate if the opposition manages to create attacking chaos. Chelsea looked vulnerable to crosses and there can often be space available in behind on the flanks if their attacking wing-backs are caught out of position higher up the field.

Timo Werner's woes in front of goal continue, but Christian Pulisic and Kai Havertz are impressing and provide a threat up front. Much will depend on how that double pivot of Mateo Kovacic, Jorginho or N'Golo Kante can dictate matters from the middle of the pitch.

Where Manchester City will win or lose: Manchester City have a day's fewer rest between games, having played their Champions League quarterfinal in Germany on Wednesday. Fatigue is one potential issue for City to overcome as a four-way trophy hunt can be exhausting, but expect Guardiola to shuffle his pack accordingly. City have failed to score just once this year (against Manchester United in March), so expect them to test Chelsea's defensive resolve.

They can sometimes look rattled when they go a goal down, and Chelsea will note how Leeds managed to beat them 2-1 last weekend, despite going down to 10-men. They effectively built a wall in front of their goal, allowed City's defensive players time on the ball but prevented them from unleashing more attacking options, and then hit them on the counter by playing directly over the top of City's backline.

Key players: Mason Mount is the heartbeat of this Chelsea side and is one of the form players in the Premier League. The England man is sixth in xA (expected assists) with 5.49 and has created the third-most chances (73). Pulisic is playing well with three goals in two Premier League matches and was named Man of the Match for his two-goal showing against Crystal Palace last Saturday. But Chelsea will have to contain City's creative power, so Kante will be key, as will defensive stability with Cesar Azpilicueta, the man who anchors all that together. They will look to catch City on the counter-attack so keep your eyes Werner, Havertz and Hakim Ziyech.

For City, Ruben Dias has been the key to shoring up their defence and regardless of who partners him at centre-back, he's integral to everything they do well. Joao Cancelo and Kyle Walker are arguably the best full-back duo in the Premier League at present, while midfielder Ilkay Gundogan is in the form of his life. But Kevin De Bruyne and Phil Foden are at the centre of everything City do well. De Bruyne has five goals in his last six City matches, while Foden scored a stunning winner against BVB on Wednesday. Chelsea know that if they are to fare well on Saturday, they must stop them.

Prediction: It'll be a low-scoring, nervy affair, with extra time a real possibility, but we're backing City to come through and continue their charge for the quadruple.

Leicester City vs. Southampton (Sunday, 1:30pm ET on ESPN+)

Overview: Both teams come into this off the back of painful defeats, but with different prospects and aims for the rest of the season. Brendan Rodgers' Leicester City are still firmly in the mix for a Champions League spot despite losing 3-2 at the weekend to West Ham United. But they have also had to contend with off-field strife in the last week, with three of their players stood down for the trip to West Ham due to COVID-19 protocol breaches. Hamza Choudhury and James Maddison missed out on that match after reports they attended a party at Ayoze Perez's house. The trio are back in the mix for this weekend, but it was a distraction Rodgers could have done without.

Southampton are an unpredictable quantity at the moment. Ralph Hasenhuttl's side lost 3-0 to West Brom at the weekend, meaning they have lost 11 of their last 14 top-flight matches. Hasenhuttl warned his players if they play against Leicester as they did against WBA, they have "no chance" of getting through after what he labelled a "non-performance" against Sam Allardyce's side.

Leicester booked their spot in the final four thanks to a 2-1 win over Manchester United, while Southampton eased past Bournemouth 3-1. This match has the bonus of being played in front of 4,000 local Wembley residents as one of the government's test events to get bigger crowds back this summer.

Where Leicester City will win or lose: Leicester have lost two from two since the internationals, and have lacked the intensity which saw them beat United in the quarterfinals the weekend before the break. They are finding themselves in solid positions on the field, but also have looked vulnerable at the back.

They are used to dominating possession and territory and will likely enjoy plenty of time on the ball this weekend. They also have one of the in-form players in the Premier League at the moment, with Kelechi Iheanacho on a goal-scoring run of nine in six matches. The omens are good for the Foxes -- they have never lost three on the bounce under Rodgers -- but they need the whole team to come together after a tough week on and off the field as they contest the club's first FA Cup semifinal since 1982.

Where Southampton will win or lose: Southampton's 2021 has been poor. That free-flowing, rock'n'roll gegenpressing football we saw in the latter stages of 2020 has been replaced by erratic and frustrating performances in the league. But their FA Cup form has been the outlier. They were magnificent against Bournemouth in the quarterfinals -- with Nathan Redmond outstanding -- and they hoped to ride that wave into Sunday's semifinal, only for WBA to bring them crashing back down to earth.

Self-confidence could be a big issue come Sunday, given their recent form, and while Che Adams and James Ward-Prowse have kept their form at a consistently high level, too many of their teammates have experienced a drop since the New Year. If Southampton re-find their mid-season best (like we saw in their win over Liverpool in January) then Danny Ings (whose long-term future is starting to get more airtime at St Mary's given his contract is up in 2022), Adams and Ward-Prowse can cause Leicester some headaches. That said, they will need a full team performance if they are to get through to their first FA Cup final since 2003.

Key players: Iheanacho is playing superbly at the moment for Leicester, and his two goals helped them to their 3-1 win over United in the quarterfinals. Youri Tielemans is excellent in the middle of the park, and he dovetails nicely with Wilfred Ndidi so expect them to see plenty of the ball on Sunday. They will likely be without Harvey Barnes for the weekend but should have their disciplined trio back in the mix. Also keep an eye on Wesley Fofana at the back, as the young French defender has been one of the players of the season and seen his stock skyrocket.

Ward-Prowse's set-piece prowess is a key weapon in Southampton's arsenal, and he leads the Premier League with four goals from free kicks this term. He's the focal point of their side and has contributed the most assists (five) in the league, has the second most recoveries (234) and has attempted the sixth-most passes (2022 in the Premier League). Ings has nine goals for the season so don't forget about him, while Adams is also impressing up front. Finally, Redmond has found some form with three in three while centre-backs Jan Bednarek and Jannik Vestergaard are solid.

Prediction: Leicester City should have too much for the Saints and book a place in their first FA Cup final since 1969. They'll need to come together after a difficult week but will live up to their tag as pre-match favourites.