Players can only leave if replacements come in - Amorim

Manchester United head coach Ruben Amorim is not willing to let any players leave in the January transfer window unless replacements come in.

Kobbie Mainoo and Joshua Zirkzee are both keen for chances to play more regularly over the second half of the season. Mainoo still wants to go out on loan, while Zirkzee has been linked with a return to Italy.

However, even when his squad is bolstered in the middle of next month by the return to fitness of skipper Bruno Fernandes and Bryan Mbeumo, Amad Diallo and Noussair Mazraoui returning from the Africa Cup of Nations, Amorim does not believe there are enough players in his squad to cope with a reduction in numbers.

"It's going to be hard for someone to leave the club if we don't get a substitution," he said.

"We are short. Even with the full squad we are short for something that can happen.

"We are a club with a big responsibility. We are dealing with all these issues and in [the media's] heads, in my head, in everybody's head, we need to win every game. It doesn't matter. There are no excuses."

Amorim will be without seven senior players for the Boxing Day match against Newcastle.

Mainoo is still sidelined with a calf problem, while defenders Matthijs de Ligt and Harry Maguire also miss out.

Amorim has already said it is possible United may sign someone in January, although that will not be Bournemouth's Antoine Semenyo, who is set to join Manchester City instead.

In theory, an upgrade in midfield as a replacement for Zirzkee or Mainoo may improve United as they chase a European place over the second half of the season.

Financially though, losing Mainoo may not make much sense given whoever came in would be on three or four times the 20-year-old's current salary.

Unless Mainoo returns quickly, 18-year-old England youth international Jack Fletcher will be providing the midfield competition for Casemiro, Mason Mount and Manuel Ugarte over the Christmas and New Year period.

Yet Amorim is doubling down on his view there is no point signing players if they are not part of a longer-term vision.

"We are struggling in this moment, but the club has a plan and we are going to stick with the plan," he said.

"If we have the opportunity to bring a player [in] that we think is going to be the future of the club, [he] is going to come. If not, we have Jack [Fletcher], we have Shea [Lacey] - in three weeks we'll have Amad, Noussair and Bryan, and the return of Bruno and Kobbie Mainoo."

Amorim offered no update on the contractual positions of Casemiro and Maguire, who are both free to talk with potential new clubs from 1 January.

He feels Casemiro's performances in training prove the Brazil skipper will not ease off as he counts down the days to what will be the end of his United career - unless he takes a significant reduction from his £300,000-a-week salary.

Mainoo was supposed to be learning from the former Real Madrid man but has ended up competing with him for a place in Amorim's midfield - and Casemiro has clearly won that battle.

However, despite having to defend himself repeatedly for not using Mainoo often enough, Amorim feels the United academy product will eventually be the future of the club.

"Kobbie Mainoo [has] played in different positions," he said.

"He can do [Casemiro's] position. He can play if we play with three, he can play like we play in the last game [at Aston Villa].

"The position of Mason Mount in that game, he can play there.

"He is going is going to be the future of Manchester United. That is my feeling.

"He just needs to wait for his chance. In football, everything can change in two days."