Man Utd left-back Alex Telles injured his ankle during pre-season training and missed Saturday's friendly against QPR.
Telles was in a 2-1 friendly win over Derby County last Sunday, but with the injury he has now suffered, his availability at the start of the Premier League season could be questioned.
Ole Gunnar Solskjaer told the club's website:
"Unfortunately, Alex slipped and he twisted his ankle so he'll be out for a few weeks
"We're hoping that it's not going to be too bad but he'll be out for a little while."
The 28-year-old defender also looks set to miss next week's friendlies against Brentford and Preston.
The Brazilian has played 24 times in all competitions for United since arriving from Porto last October and has made an impressive showing.