The 30-year-old picked up the knock in a training session on Monday and will now undergo a fitness test to determine whether he will be available for the remainder of the club's pre-season tour.
The Bulgarian was expected to be out to prove a point this pre-season after he was left out of the United side to face Barcelona in the Champions League final.
However, Red Devils boss Sir Alex Ferguson was full of praise for Berbatov earlier this week, after reporters asked whether he would have understood the striker wanting to leave this summer.
"Berbatov will be all right. His training has been terrific and he's a good person, a nice guy," Ferguson said.
"There were seven or eight players disappointed at not being involved in the final. Berbatov will be all right."
The former Tottenham man has made 96 starts for United since joining from Spurs in 2008.