Manchester United must send a "big signal" and tie David de Gea down to a new five-year contract, according to legendary goalkeeper Peter Schmeichel.

De Gea is out of contract at the end of the 2015-16 season and reports are abound that Real Madrid are interested in making the Spain international the long-term replacement for Iker Casillas.

The 24-year-old has been United's outstanding performer of the season, with De Gea credited with single-handedly keeping the club in the race for a Champions League place as the season enters the final third.

But the uncertainty over De Gea's future has drawn a cloud over Old Trafford and Schmeichel says if the club's revival under manager Louis van Gaal is to be taken with any seriousness, they must secure the shot-stopper to fresh terms.

"It's very important the club's best players sign new contracts to send a signal," the Dane told Sky Sports News.

"It shows that they believe in the Manchester United project and believe the club will go back not only to the top of the Premier League but also European football.

"If De Gea signs a new deal, it would be a very big signal and I'm sure everyone who loves the club would love that. Fingers crossed he will sign another five-year contract."

The future of on loan forward Radamel Falcao is also subject of intense speculation, with the Colombia international having netted just four times since moving from Monaco on a season-long loan spell.

United are undecided whether to sanction a permanent move for Falcao but Schmeichel is hopeful the player will return to his best.

"We knew when he came that he had this injury and it was his reaction to coming back that was to be the exciting part," the former United treble winner said.

"Unfortunately he's had more injuries but if he is 100% from next season then he's the kind of player that I think Manchester United would love to add permanently to the club.

"He has proven himself to be a fantastic goalscorer in the past and he's been unlucky in the last 18 months. Hopefully he can get through this injury hell and get back to what he used to be."