Manchester United are reportedly fearful that record signing Angel di Maria could be facing a spell on the sidelines.
The 27-year-old was forced off the field in the first half of Argentina's disappointing Copa America final defeat to host nation Chile on Saturday night.
Di Maria, a £59.7m capture from Real Madrid last summer, went down under no contact at the Estadio Nacional and was unable to shake off the hamstring problem.
Widespread reports suggest that the United man is now in a real race against time to be fit for United's opening Premier League fixture against Tottenham Hotspur on August 8.
Prior to his injury, Di Maria had found the net twice during Argentina's Copa America campaign.
