Juan Mata is set for several weeks on the sidelines after undergoing a hernia operation on Thursday.
The Spaniard will certainly miss United's three Premier League fixtures this week and is likely to miss the first leg of the Europa League match against Anderlecht.
He will undergo further assessments at the beginning of next week, although the Spaniard does expect to be back playing before the end of the season.
The operation was completed successfully and the initial response has been positive but Mata has not been at Carrington all week.