Sydney FC have been dealt a blow with injury ruling Socceroos skipper Lucas Neill out of their crucial A-League clash against Central Coast Mariners on Saturday.

Sydney revealed on Thursday defender Neill would be out for at least a week after he was diagnosed with a minor calf muscle tear.

Socceroos captain Lucas Neill doing a light training session on Wednesday with Sydney FC. Credit:Brendan Esposito

The setback, which came after Neill was unable to complete the morning training session, took some gloss off news that captain Terry McFlynn had been re-signed for another year.

The club has also re-signed exciting young midfielder Peter Triantis for the next two seasons and reserve goalkeeper Ivan Necevski has his contract extended for another season.