The Spain international is yet to put pen to paper on a lucrative new contract despite the shot stopper having less than 18 months remaining on his current United deal.
De Gea has been heavily linked with Champions League holders Real Madrid in recent months amid reports Los Blancos want the United man to replace Spain captain Iker Casillas.
Former Liverpool goalkeeper Reina, who swapped Anfield for Bayern Munich in a permanent move last summer, appeared to urge De Gea to stay put at the Red Devils beyond the end of the season.
“He is one of the top goalkeepers in Europe and this year he has been superb,” Reina told talkSPORT.
“Maybe Real Madrid are looking for a goalkeeper and De Gea is one of the names suggested, but I think he should be happy enough to play for United.”
De Gea helped United to Premier League title glory in 2013 after the shot stopped completed a £18m move to the 20-time English champions from Atletico Madrid in 2011.
The former los Rojiblancos man has made 158 appearances for United during his four-year stay at the Manchester club.
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