ST KILDA coach Alan Richardson rates Nick Riewoldt a "50/50" chance to play against Carlton this Sunday as the Saints captain battles a left knee injury.

The champion forward, who has been in brilliant form this year after a move up the ground, struggled in St Kilda's loss to Adelaide on Sunday with the knee problem.

He was among a number of injury concerns to come out of the heavy defeat, including Paddy McCartin (concussion), Sean Dempster (knee) and Hugh Goddard (Achilles).

Richardson remained hopeful Riewoldt would be fit to take on the Blues on Sunday afternoon at Etihad Stadium, but said the skipper would need to train strongly at the club's main session on Wednesday.

"In the past 50/50 means he's probably going to play, doesn't it? It's fair to say that he was really struggling after the game. We'll just have to wait and see how he goes, but he's amazing," Richardson said on Tuesday.

"He tends to find a way, so we'll give him every opportunity. Having said that, he'll need to do a bit tomorrow. It won't be that he doesn't train tomorrow and just gets through the captain's run, which is pretty light.

"He'll need to do a little bit tomorrow and then do a bit after that to be a chance to play."

The Saints face a challenge against the in-form Blues, particularly with a depleted backline that will lose Dempster and Goddard and is already without veteran Sam Fisher (hamstring).

Richardson forecast moving utility Sam Gilbert to a more defensive role, and also said Tom Lee and Luke Delaney could come into the team from the VFL.

"They're definitely going to come into calculation. We'll make that call on Thursday," Richardson said.

Lee has had a stuttering career at the Saints since joining the club in 2012, playing just 15 games in four seasons. Richardson said if Lee is promoted, the 25-year-old needed to take his opportunity.

"He needs to keep performing at the level below and he's doing all those things. He can't be doing much more, he [just] needs us to select him. That might happen this week, it might not," Richardson said.

"If it doesn't happen this week it's not the end of his career, we acknowledge he's heading in the right direction. There is every chance he'll come in, we'll just have to wait and see."