Jose Mourinho says he is "disappointed" Andreas Pereira has decided to leave Manchester United to join Valencia on loan rather than stay and fight for his place at Old Trafford.
The Spanish side wrapped up a season-long deal for the Brazil international midfielder late on Friday night, nearly 24 hours after the English transfer window had closed.
The 21-year-old Brazilian defied Mourinho's express advice when he sought, and accepted, a temporary move to La Liga side, having spent all of last season on loan at La Liga club Granada.
"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." Mourinho said, as reported by ESPN.
"He has the potential to be fighting for a position, opportunities and to be a Manchester United player.
"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 January 1, so it is not a drama but a decision which disappoints me a little bit."
Pereira, signed as a youth player from PSV Eindhoven five years, has yet to start a league game for United but is so highly regarded that he was handed a new, long-term deal by Mourinho this summer, just as he decided to move elsewhere.
The Belgium-born Brazil international has been at Old Trafford since the age of 16 and made 13 appearances for the first team. He was also loaned out last year, scoring five times in 35 league games for Spanish club Granada.
Pereira committed his future to United by signing a new two-year contract last week after sealing a season-long move to the La Liga club on the last day of the Spanish transfer window.
The midfielder has played 13 times for the Red Devils' first team, scoring once, but has failed to make a matchday squad so far this season.