David de Gea, Manchester United's sprawling, spectacular superhuman they simply can't afford to lose

De Gea is often the difference between United winning a game they would otherwise have drawn - Jose Mourinho cannot afford to lose him at any price

When Jose Mourinho pauses before answering a question, the response that follows is usually a significant one, and when the subject of David de Gea was raised after Tuesday's victory over Young Boys, the Manchester United manager took a moment to consider his words.

Nobody could disagree with his answer. "He's a world-class player," Mourinho said. "He's the best goalkeeper in the world, and if our ambitions are to be a big club, to be a winning club, you need the best goalkeeper in the world and you need also some other players the best in the world.

"In this case, we have the best goalkeeper in the world and I know he wants to stay," he then added. "I know his agent is happy to do what the player wants and I also know the board wants him to stay and they are working on that. Hopefully, sooner or later they reach a good conclusion."

Mourinho had, about three-quarters-of-an-hour earlier, witnessed a De Gea save that was as important as Marouane Fellaini's stoppage-time winner in booking United's place in this year's Champions League knock-out stages.

De Gea cannot have seen much of the Ulisses Garcia's 70th-minute shot which came through a pack of bodies, deflected off Kevin Mbabu and perilously trickled towards the United goal, though still he scooped it away, just as it began rolling on the white paint of his goal-line.

It was the type of save that De Gea now routinely makes - sprawling, spectacular and vital - but also the type that United are increasingly in grave danger of losing.

De Gea's current Old Trafford contract will expire at the end of the season, though United can automatically extend his existing terms by a year until the summer of 2020.

With effectively 18 months to run, United need their goalkeeper to sign new terms quickly lest he leaves cheaply this coming summer, if not for free the year after. Mourinho simply cannot countenance losing him for any price.

For a manager who seeks out dependable players, De Gea has been his only consistent performer over the course of his two-and-a-bit years at Old Trafford. Every other member of Mourinho's squad has fallen below his exacting standards at some point, bar his goalkeeper.

De Gea was on hand to bail United out (AP)

As on Tuesday, De Gea is often the difference between United winning a game they would otherwise have drawn. He is often the difference between a draw and a defeat too and every now and again, he is the reason United merely lose a game rather than being annihilated.

In the Premier League last year, the numbers under United's hood suggested their excellent defensive record was largely down to De Gea. United would have been approximately 12 goals worse off if they could only rely on your common-or-garden goalkeeper rather than a superhuman.

Mourinho knows this well enough, hence his efforts to make De Gea feel as wanted as possible of late. Last week, the United manager happily reopened hostilities with Iker Casillas in order to come to the defence of his goalkeeper, "the best in the world".

Then came Tuesday's carefully considered answer, with the repetition of the "best in the world" line, and the linking of De Gea's vital save with Fellaini's winning goal. "I have to reunite the goal we scored with David's save," Mourinho said. "I think without David's save, no winning goal."

De Gea was once again outstanding for United (EPA)

By far the most telling part, though, was the United manager's deliberate suggestion that De Gea is willing to sign new terms anyway - despite the team's manifest problems on-the-pitch, despite interest in his services from both Paris and Turin.

If we are to take Mourinho at his word on this - he and De Gea share representatives, of course - and if we are to believe that De Gea's first choice is to stay and succeed in Manchester, then the question is whether United wish to match those ambitions?

Tuesday night, like so many De Gea performances before it, suggested they cannot afford not to.