Manchester United have triggered a clause to extend Juan Mata's contract by one year to the end of the 2018-19 season.

The Spaniard's deal was due to expire at end of the current campaign, but the Red Devils have opted to activate their option to prolong his stay by a further 12 months.

United boss Jose Mourinho, who sold Mata to United from Chelsea in January 2014, spoke of his player's importance to the team at a press conference on Tuesday.

"Mata is very important," the Portuguese said ahead of the Red Devils' Premier League trip to Tottenham Hotspur on Wednesday night.

"When I arrived one-and-a-half years ago, [they said], 'Mata is in trouble, in trouble, in trouble', and now he's getting an extension of one more year.

"An important player for me; important player for the club; important player for the other players."

Mata, meanwhile, told MUTV: "I still feel very happy and very proud to be part of this club. I think everyone that belongs to Manchester United should feel privileged, and that's how I feel.

"I'm happy with everyone at the club and, obviously, with the manager and my teammates. Once you are part of this club, your football career is not the same; it changes, because this is one of the biggest clubs in football history.

"Every day I try to tell myself how lucky and how privileged I am, try to take advantage of every single training session, and try to see how important it is to be a Manchester United player."

Mata has made 172 appearances for United, scoring 39 goals.