The 27-year-old’s future has been repeatedly questioned since he came close to joining Real Madrid three years ago and United are desperate to keep hold of the Spain international.
Courtois’ move from Chelsea to the Bernabeu last week has taken his most obvious destination out of the equation, boosting United’s hopes of agreeing a new contract with De Gea.
The Spaniard’s current deal expires next summer with a further year existing as an option to be triggered by the club.
The market for keepers has spiralled considerably in the past year, with Jordan Pickford costing Everton £30 million last summer when he was both uncapped by England and recently relegated, and the world record broken twice in the past month.
First Alisson Becker moved from Roma to Liverpool for around £66m, then Chelsea trumped that by replacing Courtois with Athletic Bilbao’s Kepa Arrizabalaga for £72.1m.
That makes the £18.9m De Gea cost in 2011 look paltry by comparison but United’s interest has long been in locking down a long-term stay rather than cashing in.
In the aftermath of Manchester United’s 2-1 opening night Premier League win over Leicester on Friday, Pogba appeared to cast his United future into doubt.
“There are things, and there are things that I cannot say, otherwise I will get fined,” said the Frenchman, who was named captain by his manager.
Mourinho is expected to address the issue when he next speaks this week ahead of the game against Brighton on Sunday, although it is understood that Pogba’s words came out the blue for the United manager.
Mourinho expects his players to raise any issues that they have with him to his face.
The pair get on well together, Mourinho believes. There have never been any clashes on the training ground.
Having suggested Pogba had lack of focus during his time at United, Mourinho would have expected any comeback from the player before that first game against Leicester for which the player returned to the team ahead of schedule.
Mourinho felt making him captain on the night was enough of a signal of faith in the player despite the comments by both sides over the course of the summer.
The tension between the two has chiefly been created, Mourinho believes, by the player’s agent Mino Raiola while within the training ground there are no issues between the £89 million man and his manager.
When Mourinho made his comments during the summer about a World Cup finals being the “perfect habitat” for Pogba, because he was “completely isolated from the external world”, it was the situation with Raiola that was central to his thinking.
Whether Barcelona, who seem to be Pogba’s chief suitor, could afford the kind of fee to sign him either in this window or the next remains seriously in doubt.
United believe that any pursuit of the player that continues to the end of the transfer window will be purely for the purpose of suggesting that Barca have ambition – if not the resources.
Barca’s preliminary financial figures for the year 2017-2018 were published last month and show that the club made an operating profit of €31 million for that period, despite selling Neymar for around €198m – all of which was paid up front as his release fee.
The cost of Philippe Coutinho from Liverpool and Ousmane Dembele from Borussia Dortmunds is spread over the course of their five-year contracts.
With profits of €31m it begs the question what costs have swallowed up the remaining €90-€100m from the Neymar deal, with Barca, like Real Madrid, also struggling with a wage bill of around €400m annually.
Pogba, who scored in United’s season-opening win against Leicester on Friday as captain, is reported to have told of his desire to leave Old Trafford amid speculation of a strained relationship with boss Jose Mourinho.
The World Cup winner did little to ease the situation after stating that there are things he “cannot say otherwise I will get fined”.
Brown is intrigued by the midfielder’s cryptic statement, but thinks he will let his football do the talking.
“I’d like to know what he thinks he can’t say, but he is still a Man United player,” Brown told Press Association Sport.
“I think Pogba did well the other day, he had a great World Cup obviously.
“I don’t really know too much about what’s been said or talked about but he is a Man United player and I am sure he is happy there.
“He scored a goal on Friday – the season has started now so he will just get his head down and play football.
“I think he is brilliant, he has to try and do his best for the team like any other player.”
Pogba is not the only one who is discontented as boss Mourinho was frustrated at the club’s failure to bring in extra defensive bodies ahead of the transfer deadline.
Fred, Diogo Dalot and Lee Grant arrived but United were unable to bring in a centre-back despite keen interest in Harry Maguire, Toby Alderweireld and Jerome Boateng.
Brown, who played for United over 350 times, does not think the defensive crisis is as bad as people think.
“The problem was last season a lot of the defenders were injured, he had to swap and change a lot,” the 38-year-old added.
“Fred was a good signing, he has fitted in straight away. Some teams have bought players and some teams haven’t.
“If a player is not there to be bought then sometimes it doesn’t work. People are always saying about defenders, but they had the second best defensive record last season.
“It’s good if you can boost any position, because it’s good to challenge for positions, it makes you play better and gets the best out of the players.”