West Ham's medical team are liaising with their Mexico counterparts regarding the injury Edson Alvarez sustained at the Copa America.
Hammers midfielder Alvarez, 26, collapsed clutching his hamstring in the 30th minute of his country's 1-0 win against Jamaica in their group match, then limped off the pitch in tears.
"We're going to wait a couple of days to do some testing on him and to know well what he's got going on," said Mexico manager Jaime Lozano.
"He's extremely important. He's a leader, he understands the game well. He's important on the pitch and in the locker room as well.