The 22-year-old stopper came under criticism during the weekend after his weak clearance allowed Tottenham Hotspur to equalise in injury-time at White Hart Lane.
The youngster has been inconsistent since his £18.5 million move from Atletico Madrid in 2011 and manager sir Alex Ferguson tends to rotate him with Anders Lindegaard.
De Gea has been praised for his talent in a number of games but the youngster seems to have failed to adjust to life in England, which has indirectly affected his game.
United are believed to be interested in Stoke City keeper Asmir Begovic but face competition from their rivals Manchester City. However, Stoke's £12 million valuation for their Bosnian stopper may drive off United's interest.
Begovic, 25, can immediately replace under-fire De Gea at United but will face Joe Hart at Etihad Stadium.