Belgium manager Roberto Martinez fears Manchester United midfielder Marouane Fellaini may have suffered knee ligament damage in his side's World Cup Qualifier against Bosnia Herzegovina.
Fellaini was moving with some difficulty before signalling to the bench that he was hurt and laying on the ground with his side 1-0 up.
He was treated briefly by medical staff and appeared to indicate there was a problem in his left knee, before being replaced by Anderlecht's Leander Dendocker.
And after the game, Martinez said: "We are all worried about Fellaini. We fear that there's ligament damage."
A Belgian FA official also confirmed the injury, and said: "It is something to be worried about on first sight. Ligaments, left knee. More news tomorrow."
Bosnia equalised immediately after Fellaini was withdrawn and went 1-0 up just before half-time but Belgium recovered to win 4-3.
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Fellaini has become a key player for United in recent weeks and has scored four goals in his past five appearances for the club.
United will be hoping for a positive prognosis on the midfielder after the weekend with their next Premier League fixture against rivals Liverpool on October 14, live on Sky Sports.