Chelsea forward Kevin de Bruyne is to return to London for a scan after injuring his knee during Sunday's 4-1 win over a Malaysia XI in Kuala Lumpur.
After creating the first goal, the Belgian was injured while scoring the second at the Shah Alam Stadium.
De Bruyne, 22, fired in a fine volley but fell awkwardly and immediately called for medical assistance.
However, after the match manager Jose Mourinho said he is optimistic that the problem is only minor.
"When he was on the floor and asking for a change, we thought the worst," said Mourinho.
"But the first assessment by the doctor was that it was not the ligaments for sure, and if it is something in the meniscus then it has to be a very small injury.
"So we believe it is not an important injury and hopefully it isn't because the kid is a fantastic player. He's showing to me in training that he is going to be a key man on the pitch."
De Bruyne will miss Thursday's game against Indonesia All Stars but Chelsea are confident he will rejoin the squad when they travel to the United States for the concluding games of their pre-season tour.
The Blues play Inter Milan in Indianapolis on Thursday, 1 August in the first of four scheduled games in America.
De Bruyne joined from Belgian side Genk for £7m in January 2012 but has yet to play a competitive match for Chelsea.
However, an impressive season on loan at German side Werder Bremen enhanced his reputation and his return to Stamford Bridge has been keenly anticipated ahead of the new season.