West Ham defender Aaron Cresswell will miss up to four months due to a knee ligament injury, the club has confirmed.
The left back, who has missed just one Premier League game in the past two seasons, went for scans after being hurt in his side's friendly victory over Karlsruher in Austria on Saturday.
"West Ham United can confirm that Aaron Cresswell will be out of action for three to four months after suffering a knee ligament injury," the club said in a statement.
"Head of Medical and Sports Science Stijn Vandenbroucke explained that Cresswell had undergone a scan and will consult a specialist in central London early next week. The medical team will then take a decision whether or not the defender requires surgery."
West Ham also said it is in touch with the Argentine Football Association over Manuel Lanzini, who sustained a knee injury in Argentina's Olympic warm-up fixture against Colombia and could well miss the tournament in Rio.
"We are in close contact with Manuel and the AFA, who have started a late-release replacement procedure with the IOC [International Olympic Committee]," Vandenbroucke told the club's website.
"Until he has been assessed by the IOC, he cannot be replaced, but after this process has been completed we want him to return to England to be assessed by our own medical staff as soon as possible."