This is according to the Express, who understand that Real Madrid boss Carlo Ancelotti wants the Spain international to come to the Bernabeu in order to compete with Keylor Navas for the No. 1 jersey.
Arsenal and Liverpool keen on Casillas
The much-maligned Iker Casillas has been Ancelotti’s first-choice keeper at the start of this season - having started six of Real Madrid’s seven La Liga fixtures - but is not expected to be at the Bernabeu for much longer.
Arsenal and Liverpool are both reportedly keen to sign the 33-year-old, who has even been jeered by pockets of his own supporters this season, in January.
However, United boss Louis van Gaal will be desperately hoping that Casillas stays put with the reigning European champions, to avoid the possibility of De Gea’s head being turned by the prospect of playing for arguably the most glamorous club on the planet.
De Gea's contract expires in 2016
De Gea - who began his career with Real’s city rivals, Atletico Madrid, before joining the Red Devils in a £17.8 million deal in the summer of 2011 - is yet to sign a contract extension at Old Trafford, even though his current deal expires in 2016.
It’s believed that United plan to offer £25 million-rated De Gea a new long-term deal, worth around £90,000-a-week, but a shock return to Spain may appeal to the Madrid-born star.
Manchester United’s number one goalkeeper produced one of the best performances of his career last weekend against Everton to earn the Red Devils a hard-fought 2-1 win, and is widely considered one of the Premier League’s best, alongside the likes of Thibaut Courtois and Joe Hart.
The 23-year-old is expected to be Spain’s first-choice keeper for the next decade when he finally managed to displace Casillas, who could lose his No. 1 jersey at both club and country to the Red Devils’ ace.
Manchester United can't afford to lose De Gea
Losing De Gea would be a catastrophic blow for Manchester United, who know that replacing the Spaniard with a goalkeeper of similar quality would be near enough impossible.
The 20-time English champions have worked wonders with De Gea since he arrived in England three years ago and will do everything in their power to keep him at Old Trafford.
But few players are able to resist the lure of Real Madrid - and it may prove even more tempting for a player born and raised in the Spanish capital.
Van Gaal, it seems, may soon have a huge job on his hands convincing De Gea that he belongs in Manchester rather than Madrid.