Croatia captain Niko Kovac is facing a race against time to be fit for Sunday's game with Japan.

Kovac was replaced by substitute Jerko Leko in the 41st minute if Croatia's World Cup opener against defending champions Brazil, a match won 1-0 by the Latin American side.

Coach Zlatko Kranjcar initially hoped that Kovac, who has a thigh injury, would be able to play against the Japanese but the midfielder is still not able to train normally.

If he does not play, Leko is likely to be his replacement again.