ST KILDA champion Nick Riewoldt may only miss a couple of matches, with the knee injury he suffered against Melbourne on Saturday not as serious as it was first feared.

Scans revealed on Sunday that Riewoldt had no structural damage to his right knee after he hyperextended it late in the fourth quarter of his side's 30-point loss to the Demons.

Saints football manager Jamie Cox said on Monday the club would treat Riewoldt's injury symptomatically, easing him back into training after the pain starts to subside.

"He'll still have some time off, but hopefully only a week or two now," Cox told RSN 927.

"Our doctors are reasonably positive about trying to get him up and about and even running lightly by the end of this week.

"Hopefully this is something he can manage and get up and about pretty quickly."

Young forward Paddy McCartin could replace Riewoldt in the side after shaking off hamstring tightness.

McCartin was a late withdrawal from the game against the Demons but kicked three goals in the first half of a VFL practice match against Port Melbourne on Sunday to put himself back in the selection mix.

"He was actually passed medically fit, which is our doctors' job, and then it becomes Richo's (Saints coach Alan Richardson) job to determine whether or not he was fit to perform at AFL level and get through a full game.

"The call was made that we were not prepared to take that risk so at this stage of the year let's just park him for the moment and get him ready for this week."