United are still in two other knockout competitions, with the first leg of their League Cup semi-final against Hull City this coming Tuesday and a Europa League round-of-32 tie against Saint Etienne in February.

With fixture congestion a significant possibility, Mourinho must decide whether to make changes against Reading, a team who are third in the Championship and managed by former United favourite Jaap Stam.

Mourinho is clearly already thinking about rotation, having made five changes for Monday’s 2-0 win at West Ham.

He is likely to have midfielder Michael Carrick available again after recent illness, while captain Wayne Rooney is back in training after missing three matches with a thigh problem.

Centreback Eric Bailly is unavailable, having joined up with the Ivory Coast for the Africa Cup of Nations.

Carrick has been a key figure during the recent upturn in form, impressing in a deep midfield role and allowing Paul Pogba to focus more on attacking.

Whatever side the manager puts out, defender Daley Blind is confident that it will be able to cope, citing the United squad’s strength in depth.

“It’s a very important period. We have a very fit squad and I think we need everyone because we have a lot of games,” Blind said.

“I think that competition for places makes the team better and better. Everyone wants to fight for his place and when the competition is high, you have to perform and you lift each other’s performances. It’s good for the team.”

Stam’s return to Old Trafford will inevitably revive memories of United’s treble-winning campaign in 1999 when Alex Ferguson’s side completed a clean sweep of the Champions League, Premier League and FA Cup.

The Dutchman was an integral part of that team but left the club two years later in controversial circumstances after falling out with Ferguson over the content of the player’s book.

“It would be nice to have a warm welcome,” Stam said. “I had a great time over there. I’ve loved the fans, the club.

“It was a very important period in my career. I haven’t been back on an occasion like this so it’s good to be back, it’s good to play over there.

“But it’s not about me, it’s about the team and hopefully we can be a surprise.”

Stam’s appointment at the Madejski Stadium last June marked his return to English football and after an inconsistent start to the season, Reading have emerged as one of the main contenders for promotion to the Premier League.

“We’re not going to change how we think and our philosophy,” he said.

“Certain details we can change but our belief is possession. We still want to play. We’re not going to change our style of play.”