ST KILDA coach Alan Richardson says his skipper Nick Riewoldt will almost certainly play on if he continues his excellent form.

The 33-year-old is out of contract at the end of the season and has battled a degenerative left knee in the last stage of his career.

Three first-half goals and 14 marks for the match saw him finish as arguably his team's best player.

"He's been in good form all year. He looked so dangerous early in the game that we just wanted to keep him (forward), but he gets behind the ball for us if need be.

"If the season stopped right now, we would want Nick to keep playing. (He'll play) as long as he still has the passion and the desire to play the game, and to lead strongly.

"I'd be surprised if we're not wanting him to play on."

The six-time club champion hurt his right ankle last Sunday against GWS but Richardson said Riewoldt was always a near-certainty to play.

"He is such a resilient person, that perhaps with the exception of the whack over the head against Adelaide last year, I just think he's going to play," Richardson said after the 39-point win against Melbourne on Saturday at Etihad Stadium.

"He was pretty confident really early (about playing against the Demons). He didn't do a lot of training on the Tuesday (but) did just about everything on the Thursday."

Through the season he has shared his time between the wing and attacking 50, but Riewoldt played closer to goal on Saturday.

His presence up forward was particularly important with Paddy McCartin left out of the side.

Riewoldt's ranking of first for marks per game and 11th for goals per game attests to his strong form.

The influence some of St Kilda's lesser lights had on the game stood out for Richardson.

Tim Membrey lined up for the first time this year and kicked five goals while Jade Gresham laid four tackles and kicked a goal.

"That's probably as good as our younger guys have played as a whole. Our older guys were still strong, but we didn't need them to be as dominant," Richardson said.

"Gresham didn't get big numbers, but I thought his physicality and his want to defend were pretty strong.

"It was a bonus that Membrey kicked five. I was happy with his work rate and his contest."

Midfielder Blake Acres was one who Richardson was keen to heap praise on. Acres finished with 28 disposals and two goals in his third game for the season.

"He didn't get everything right, Blake, but for most of it he was really positive and ran very hard for us," Richardson said.

"More than any other player, he's committed to making sure he works on his game.

St Kilda faces the undefeated North Melbourne at Etihad Stadium next Sunday.