St Kilda stalwart David Armitage could undergo surgery on his troublesome groin after managing just one game in his AFL return.
The important midfielder pulled up sore after last week's win over Collingwood and has been ruled out of Sunday's clash with Geelong at Etihad Stadium.
Armitage has struggled with a persistent groin niggle which has limited him to two senior games this season.
Coach Alan Richardson says the 28-year-old will undergo scans in coming days and is likely to face extended time on the sidelines.
"We haven't been able to get a lot out of Dave - even when Dave has played, he's struggled a bit, and he'll go out for a while now, unfortunately," Richardson said on Friday.
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"He's still pulling up really sore after games so he'll have to have some tests. We won't really know the extent of it until he has those scans, which (from) my understanding will be about the middle of the week and we'll have more information then.
"It looks like he's going to possibly need to have a bit of corrective surgery but if not, at least an extended rest to make sure that we get it right."
In better news for the Saints, prime-mover Jack Steven will return after missing their past two games with a punctured lung.
The three-time best and fairest winner looms as a key addition to the St Kilda engine room ahead of a battle with Geelong superstars Patrick Dangerfield and Joel Selwood.
"We've been up against some strong midfields the last few weeks without Jack," Richardson said.
"It's brilliant to have him back in the team. He gives us real energy and he's a very dynamic midfielder with his combination of his inside work and outside work."
St Kilda will make at least one more change, with ruckman Billy Longer to play for the first time since August 2015 in place of Tom Hickey.
Hickey was sore after last week's game and was listed as managed but Richardson confirmed the decision was partly down to his form.
The Saints have started the season with a 2-2 record, and Richardson admitted their best performance had probably come during their round two loss to West Coast rather than in either of their wins.
"We think our footy's been reasonable without being great. We've been able to get a lot of opportunity in front of the ball without being able to capitalise," he said.
"We think we're heading the right way and Geelong will be a real challenge."
