Such performances have led to admiring glances from Real Madrid, where De Gea would now be playing his football was it not for a deal collapsing acrimoniously in September 2015.

Talk over recent months suggested another move from the Spanish capital was imminent, although United always remained confident of keeping him.

United boss Mourinho now says there is no chance De Gea will leave this summer - and suggested Real may have burned their bridges.

"I can guarantee that he's not going this season, that I can," Mourinho said ahead of facing his former club in the International Champions Cup at Levi's Stadium in Santa Clara.

"And my feeling is that it will be very difficult for him to go.

"It will be very difficult for him to go because he's a very honest boy, very straight.

"He was contacted for a long time, the club was closed. Then we open because I always have this feeling of when a player has a desire to go I don't like to stop players to go because in the end you don't get from them what you expect from them if they want to move and they don't move.

"So we open it and then they decide to close, and I don't think the feeling for him is very, very good.

"I see him really happy and focused and working better than ever, so for me 100 per cent he stays with us."

United are in an enviable position regarding their goalkeeping situation given there are few better back-ups than Sergio Romero.

Earlier this year Mourinho said both shot-stoppers were "equally important", with the Argentina's No.1 fine form seeing him start the Europa League triumph and earn a new deal.

"I'm impressed with (Romero) but I'm also impressed with David," Mourinho said. "I think the best thing that could happen to David was the way Romero played last season because until then David was clearly a safe man, an undoubtful choice - and after what Romero did last season, David thinks he's training in another way.

"David is much better now than before and he has amazing conditions to progress, so to have both at the level they can be is fantastic for me and gives me the chance to choose the players in relation to their moment, in relation to the qualities of the opponent because obviously they are different goalkeepers.

"But both very good and for Joel (Pereira) to be learning with them and playing with us is good.

"Tomorrow I play Romero, David, 45-45, and not just them three but also Sam Johnstone showed at Aston Villa that he is a good goalkeeper, a good young goalkeeper with potential, so we are really good in goalkeepers."

Asked if he would select a goalkeeper specifically for European matches, Mourinho added: "I think I will decide on goalkeepers match by match, yeah.

"It depends on the opponent, it depends on form, it depends on the match we have in the Premier League before and after. It depends on many things.

"I'm not going always to be jumping from keeper to keeper, match, match, match.

"No, but I will try to analyse and the only thing I can say is that we all, not just me, trust both goalkeeper a lot."