PROMISING Greater Western Sydney defender Jeremy Finlayson will miss the next 4-6 weeks with a knee injury.

The 20-year-old damaged ligaments in his right knee in Saturday's reserves practice match at Tom Wills oval, just over a week after he made his senior debut in the Giants' NAB Challenge match against the Western Bulldogs.

Finlayson is another product of the club's academy system and while not in the frame for a spot in Leon Cameron's team for round one, he's an impressive prospect.

In better news, athletic defender Nick Haynes is back training with the main group after recovering from groin surgery he underwent in December.

Haynes struggled through the second half of last season and his return means Cameron could have his best 22 fit and ready for the start of the season.

Stephen Coniglio (hamstring) and Devon Smith (knee) could return to play the Brisbane Lions in the Giant's final NAB Challenge on Sunday should they prove their fitness at training on Thursday.

Ruckman Shane Mumford (ankle) is also a chance, although he's unlikely to be risked after re-injuring the joint he had reconstructed last year against the Sydney Swans on Friday night.

Strong backman Tim Mohr is on track for a return early in the season after having his second knee reconstruction in two seasons last year, while young midfielder Paul Ahern has returned to the club after having the same operation almost a month ago.