Goalkeeper De Gea was again linked with a move to the Bernabeu in the summer, two years after a transfer collapsed at the last minute.

After the move failed to materialise, the Spain international signed a new contact that keeps him at Old Trafford until 2019, with the option of another year.

Herrera said De Gea was happy at the club, adding: "I can see him staying here for more years, but we need to win titles to keep him with us. That is what we did last season.

"David is really happy at the moment because we are fighting for everything. We won three titles last season, and the FA Cup the year before, and that is what he wants.

"Real Madrid are going to talk about it every summer because he is the best keeper in the world. But we don't think we are far from Real Madrid -- we won three titles last season, the only English team to do it.

"We are going to enjoy having him here and try to keep him at the club for as long as possible."

The midfielder added: "If he is not a legend already, he is not too far away from being one of the legends of the club."

United romped to a 4-0 win over Everton at Old Trafford on Sunday, with De Gea denying both Gylfi Sigurdsson and former colleague Wayne Rooney when the score was 1-0.

And Herrera said: "For me, he is the No. 1. I respect all the keepers like Manuel Neuer, Gianluigi Buffon and Marc-Andre ter Stegen, but David right now is the No. 1 in the world.

"He is very calm, and that is the thing that always surprises me the most about him. He has that quality. It comes from God. He makes a difference.

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"It makes a difference when you have a keeper who wins you points. He is one of the few keepers who can give you points."

De Gea's clean sheet against Everton was his 100th for the club in 276 appearances, and his fifth in seven games this season.

Stoke's Maxim Choupo-Moting is the only Premier League player to have scored against him this season, and Herrera said: "I think he is in that position now where he intimidates strikers.

"He has been in the club six years and the first six months he told me were difficult for him, but after that he has been the best.

"Every single season he has been the best and you know how difficult it is for a keeper in the Premier League because even sometimes the referees don't give you some fouls.

"He makes some unbelievable saves. Even in training we end up laughing at times, because we try to score and it is just impossible."