Everton boss Ronald Koeman insists Davy Klaassen will come good.
Former Ajax man Klaassen, 24, has struggled to keep up with the pace of the Premier League so far since his big-money move this summer.
Speaking to De Telegraaf, Koeman said: “For Davy it has not been easy start for him at Everton, but I have no doubt about his qualities.
“There are so many other examples of players in the Premier League who were best in their country and moved to England because they were ready for a higher level but once they arrived it turned out that they needed a period of time to adjust.
“In terms of pace, aggressiveness and the physicality especially for a midfielder [it's difficult].
"No matter how good you are, you won't be at your top at once when you are in English football.
“There are bigger players who moved to bigger clubs who needed a whole season.
“If you saw and heard the criticism he received in his first season, that was unprecedented and he also had his difficulties.
“Now he is playing at his level and is important for Manchester United every week but only after one season in the Premier League."