Sydney FC Coach Terry Butcher has stated marquee signing Dwight Yorke is "busting a gut" to be fit for the opening match against the Central Coast Mariners at Aussie Stadium on Sunday.

Yorke resumed full training today and is also doing extra sessions in order to lift his fitness levels before Sunday's opening match of Sydney FC's Hyundai A-League title defence.

The Sydney FC Captain has recovered from a strained tendon in his groin and after two weeks of intense physiotherapy and rehabilitation is back training with the squad, six days out from the opening game.

"Dwight has been working hard on the injury to get it right and he is now back training with the squad," Butcher said. "He has been busting a gut to get ready for the game. He doesn't want to miss out on what will be a big day for the club.

"Dwight has been pushing himself hard, in fact too hard and that is what set him back with the injury. He was doing too much but he is back on track and we are still very hopeful he will be fine to play on Sunday.

"I will make up my mind on Sunday and if he is right to play it will be hard to leave him out."

The Trinidad & Tobago World Cup star also put to bed rumours that he may not complete the season with Sydney FC, telling the media at the Hyundai A-League launch he "had every intention of fulfilling his two year contract".

"I am back at Sydney FC for the second season and I am happy to be back," Yorke said when asked to ease the minds of Sydney FC fans. "I signed for two years and I am back to fulfill the second season.

"When I came to Sydney FC, I came here happily and excitedly to play for two years, and we are now ready to start the new season. I am looking forward to it and I am working hard on my fitness to be ready for the game on Sunday.

"We face a tough challenge to retain the title. All the teams have strengthened, as we have, but as the Champions everyone will be out to beat us. From my experience in the UK it is harder to defend a title than it is to win so we will have our work cut out for us."

Sydney FC takes on the Central Coast Mariners at Aussie Stadium on Sunday with the match due to kick off at 5pm.