Sydney FC midfielder Milos Ninkovic is in doubt to face Kashima Antlers in the Sky Blues' crucial Asian Champions League match on Wednesday night, but will be given up until just hours before kick-off to prove his fitness.

The Serbian playmaker has not resumed full training since Sydney's 2-1 loss to Newcastle Jets on Saturday night after suffering a minor muscle problem.

Fitness focus: Milos Ninkovic is being given the opportunity to prove he is ready to play. Credit:Brendan Esposito

Ninkovic did not train with the squad during final preparations on Tuesday, remaining with the club's physio and conditioning staff away from the rest of the team.

With Ninkovic in doubt, Sydney FC coach Graham Arnold will contemplate a reshuffle potentially shifting David Carney into a more advanced role on the wing, with Michael Zullo set to return to left back after missing the last two games due to injury.