MYSTERY surrounds star forward Toby Greene's foot injury after he was listed as an out from Greater Western Sydney's side to take on Brisbane on Saturday.

Coach Leon Cameron said the club did not yet know the extent of Greene's injury.

"I can't answer how severe the injury is, because we're probably going to need the next 48 hours to find that out," Cameron said.

"Today and Monday we'll explore what's actually wrong with his foot.

"He attempted to train on Wednesday, after he pulled up a little sore after the game last weekend and that didn't go to the level that we wanted to, then he pulled up fine yesterday and we tested it again and clearly he's not right.

"Is it a one-weeker? Is it a three-weeker? We'll find that out on Monday."

The 2016 club champion has had a frustrating run recently, missing much of the pre-season with a broken little toe and sitting out of rounds two and three with a hamstring injury.

Greene has kicked seven goals in his three games this season, including one last week.

The Giants will be looking to rebound from a disappointing draw with St Kilda last week when they kicked 9.19 and conceded the last three goals of the match.

They're favourites coming up against the Lions, although the omission of Dawson Simpson means the ruck battle will be intriguing.

It leaves usual key forward Jon Patton, supported by a handful of pinch-hitters, as the man to take on in-form Stefan Martin.

The Lion is averaging 35 hit-outs and 20 disposals a game this season.

"Clearly Stefan Martin is an outstanding ruck. You could argue that (Collingwood's Brodie) Grundy and Martin are probably the best two ruckmen in the competition," Cameron said.

"In terms of getting the ball, they follow up and actually play as extra midfielders.

"So we've gone in with a different philosophy. Patton is probably going to play a lot more ruck time, we'll discuss (Harry) Himmelberg, we'll probably discuss (Adam) Tomlinson [and] even in our back end we've got Aidan Corr."

Homegrown midfielder Nick Shipley will make his debut on Saturday, the first GWS Academy player to do so.

"It's a really good story … the story of coming out of Campbelltown," Cameron said.

"About when the Giants arrived at Western Sydney, he probably started thinking about playing AFL and jumping from another sport (soccer), and that's what he's done.

"Little did he know, six and a bit years later, he'd be playing his first game at Spotless Stadium for the Giants."