Mason Mount's 2026 World Cup dreams are all but over after the midfielder came off at the break during Manchester United's 1-0 Boxing Day win over Newcastle. Mount was replaced by youngster Jack Fletcher for the second half of Friday's narrow victory on just his 23rd league start since he left Premier League rivals Chelsea for Old Trafford back in 2022 .Patrick Dorgu scored the only goal of the game in United's narrow triumph over Eddie Howe's Newcastle side, the Dane firing past Aaron Ramsdale midway through the first half. The Magpies were arguably the more dominant of the two sides in Manchester on Friday night but the were unable to find a breakthrough once they went behind to Dorgu's fine strike.However, it was Mount's withdrawal at the break that proved a concern for United as Ruben Amorim's side battle an ongoing absentee crisis. United are already without key personnel having lost Bruno Fernandes to injury in the 2-1 loss at Aston Villa last weekend.Harry Maguire, Matthijs de Ligt and Kobbie Mainoo were also missing for United due to injury, though the trio are close to a return. Bryan Mbeumo, Amad Diallo and Noussair Mazraoui are all on international duty with Cameroon, Ivory Coast and Morocco, respectively, at the Africa Cup of Nations.And the 26-year-old's injury is a further blow for Amorim, who at full time said that Mount "felt something" that forced his withdrawal.Speaking with Sky Sports, Amorim said: "He felt something at half-time. He wanted to go, and that is also a good thing. He wanted to go in the second half, but cannot lose more players."Jack Fletcher replaced Mount for the second half, and the Portuguese boss reserved praise for the 18-year-old, adding: "Jack [Fletcher] did a very good job. It's a very important moment for any kid. He's going to hear from his father. He's going to talk a lot about a lot of things, but he needs to calm down and just praise the kid because he's really humble, works really hard, and he deserves this."United can ill-afford to lose more players as the games come thick and fast over the festive period. Indeed, they welcome table footers Wolves to Old Trafford on Tuesday night, a game that Mount is now expected to miss.Looking for smarter football bets? Get expert previews, data-driven predictions & winning insights with GOAL Tips on Telegram. Join our growing community now!Amorim opted against using his tried-and-tested 3-4-3 setup for Friday's welcome of Newcastle, instead switching to a 4-2-3-1 setup as the Portuguese boss ditched the three-at-the-back system. Amorim has previously stuck dogmatically with the formation since his arrival from Sporting last year, but sprung a surprise when Howe's side made the trip to Manchester.The 40-year-old partnered Lisandro Martinez with Ayden Heaven at the heart of the defence, with Luke Shaw and Diogo Dalot featuring at left and right-back, respectively. Manuel Ugarte and Casemiro started behind an attacking trio of Matheus Cunha, Mount and Dorgu, while Benjamin Sesko, who struck the woodwork in the victory, led the charge.Amorim had previously stated he would not change his formation. However, in his pre-match press conference, the United boss' stance on the system appears to have softened, as he said: "I think in the future we can change also the system, we can play a different way to take more quality from these players. Because I have the feeling that if we have to play a perfect 3-4-3 we need to spend a lot of money, and we need time."So you are starting to understand that that is not going to happen, so maybe I have to adapt."Add GOAL.com as a preferred source on Google to see more of our reportingUnited are next in action on Tuesday night when they take on a sorry Wolves side at Old Trafford. Wolves have lost their last 11 matches in all competitions, and travel to defending Premier League champions Liverpool on Saturday as they look to secure their first league win of the season having claimed just two points this campaign.Amorim's side then kick off 2026 with a trip to rivals Leeds, and follow up their game at Elland Road with a meeting with lowly Burnley. United are then in FA Cup action against Brighton before rounding off the month with the Manchester Derby and a visit to Premier League leaders Arsenal.