MANCHESTER -- Jose Mourinho says he is "disappointed" Andreas Pereira has decided to leave Manchester United to join Valencia on loan.

The Spanish side wrapped up a season-long deal for 21-year-old midfielder late on Friday night, nearly 24 hours after the English transfer window had closed.

Pereira signed an extended deal at Old Trafford before he left which will keep him at the club until 2019, but Mourinho insisted he would have preferred the Brazilian, who spent last season on loan at Granada, to fight for his place at United.

Pereira has played 13 times for the first team, scoring once, but has failed to make a matchday squad so far this season.

Mourinho said: "It was a personal decision that I don't agree with, a decision I don't think honestly is the best decision for him, a decision that disappoints me.

"He has the potential to be fighting for a position, opportunities and to be a Manchester United player.

Andreas Pereira will spend another season in La Liga. Photo by Manuel Queimadelos Alonso/Getty Images

"His decision can be considered a young player who wants to play every weekend but also a young player that is not ready to fight for something difficult and it's difficult to play in Manchester United's midfield.

"You have to be ready to fight for the position and I am disappointed he left.

"But was his decision, I opened the door, he has a long-term contract, we have the option to bring him back on Jan. 1, so is not a drama but is a decision which disappoints me a little bit."