JACK Billings' season is over with a hot spot in the young St Kilda forward's shin developing into a fracture.

The 19-year-old hasn't played since round 10 against Hawthorn because of the injury, and there was hope he'd return to the field at some point in August.  

But recent scans have revealed the hot spot has progressed into a fracture, which will see the No.3 draft selection put on ice for the remaining six rounds.

"Jack was due to hopefully play the last couple of rounds but further scans have showed that his stress response has progressed more to a fracture line," head physio Andrew Wallis told the club's website.

"We see that as giving him the best chance to come back and have a full pre-season and get ready for next year."

Captain Nick Riewoldt hasn't been ruled out of Sunday's interstate clash with Port Adelaide despite receiving a cork to his left calf against Melbourne.

The 32-year-old's mobility was restricted after the first quarter injury but he was still able to kick three goals and be the Saints' best player in their 37-point win on Sunday.

"He's been running around limping but he's doing really well so he's available for selection as well," Wallis said.

Riewoldt has also been struggling with the right calf strain he sustained in round 15, plus the deep cut he picked up in the leg last weekend against Richmond. 

He's played 12 games this season and hasn't missed since round eight, after he was badly concussed against the Crows on his last trip to Adelaide Oval.

Defender Jimmy Webster is also expected to be available after hurting his ribs in a heavy collision with Demons' forward Chris Dawes on Sunday. 

Webster earned plaudits from his teammates for going back with the flight of the ball and copping a heavy hit from behind from Dawes, before managing to return and play out the game.