Manchester United manager Louis van Gaal says he does not know how long it will take record signing Angel Di Maria to settle in the Premier League.
After a bright start at Old Trafford, the £59.7m signing from Real Madrid has found it difficult to make an impact.
The 27-year-old Argentine was substituted at half-time of Saturday's 2-0 Premier League win over Sunderland.
"I think it counts for all the players that we have bought, the first season is always difficult," said Van Gaal.
"You have to manage so many aspects. Not just the game, but the culture."
Van Gaal said the same applied to Di Maria's fellow new signings Luke Shaw, Daley Blind, Ander Herrera and Radamel Falcao.
The Dutchman believes it may take his summer recruits about 12 months to settle in at Old Trafford but added he could not give a "general answer".
He said: "For me, it is not a big surprise, it is more a big surprise when Di Maria adapted as quickly as possible.
"In Holland, Spain and Germany I had the same experience with players. We have to give him time, not just Di Maria but all the players. We wait and see."
Di Maria has also endured a difficult time off the pitch, with the player and his family victims of an attempted burglary while at their home in Cheshire at the end of January.