St Kilda captain Nick Riewoldt will have to show signs of improvement on Thursday if he is to play in the weekend’s AFL match against Carlton.

Riewoldt is in doubt with a knee injury and he was among several Saints hurt during last Sunday’s heavy loss to Adelaide.

Fellow key forward Paddy McCartin (concussion) is already out for Sunday’s game.

Injuries have ravaged St Kilda’s defence, with Hugh Goddard (achilles) out for about 12 months.

Sam Fisher (hamstring) suffered his injury at training last week and Sean Dempster is out of action for about a month because of knee surgery.

While the Saints would dearly love their captain to play against the improving Blues, they will want to be sure that Riewoldt has recovered enough.

Thursday’s main training run will be a key pointer.

“We’ll give him every opportunity – having said that, he’ll need to do a bit tomorrow,” said coach Alan Richardson.

“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, then pull up pretty well after that to be a chance to play.”

In Riewoldt’s favour is his amazing capacity to absorb physical punishment and keep playing.

“(He’s) 50-50 and in the past, 50-50 means he’s probably going to play, doesn’t it,” Richardson said.

“It’s fair to say he was really struggling after the game.

“We’ll just have to wait and see how he goes, but he’s amazing – he tends to find a way.”

Sam Gilbert will probably go back to defence, while the Saints could recall Luke Delaney and Tom Lee to reinforce their depleted backline.

“They’ve really been building their form,” Richardson said of Delaney and Lee.