De Gea moved to Old Trafford from Atletico Madrid in 2011 and, after a shaky start to his career in England, has now established himself as one of the best goalkeepers in the world.
The 24-year-old's deal at United is set to expire at the end of next season and, with both club and player in talks about fresh terms, Schmeichel says an agreement would represent a marker of United's intent.
"It’s very important the club's best players sign new contracts to send a signal," he told Sky Sports.
"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."
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