ST KILDA is hopeful captain Nick Riewoldt will be available to face Hawthorn next week after passing a concussion test during Saturday's win against Collingwood at the MCG.

The club is less likely to have young forward Paddy McCartin (concussion) available, however, and will certainly be without defender Dylan Roberton (knee) for the trip to Tasmania to face the three-time premiers.

Riewoldt, who has a history of concussion across 301 games, was collected high in a collision with Magpies midfielder Levi Greenwood in the second quarter and forced from the ground.   

He passed the subsequent testing but club doctors stepped in and wouldn't allow him to play out the match, which the Saints won despite having just 19 fit players for the majority of the second half.

"Our doctors made the call that they still weren't quite happy that he was right to go," coach Alan Richardson said post-match.  

"You can imagine from a coach's perspective that if someone passes a test then you're pretty anxious to get them back out there.  

"But our doctors will always have the final say and a player's welfare is paramount.

"I'm not totally sure what they saw to say he's not right to go … but he thinks he's right to."

Richardson said Riewoldt had been desperate to play out the game after a dominant first half playing on a wing, and the Saints doctors had to be "pretty strong" in their refusal to keep him out of the game.

McCartin failed his test after copping a knock to the head in a marking contest, but Richardson remained hopeful the 19-year-old would be available after playing one of his best halves since joining the club.

The No.1 draft pick took a thrilling and courageous mark running back with the flight of the ball in sustaining the injury and spent a long period on the bench before heading to the rooms for testing.   

Roberton will miss next week's clash after suffering a medial ligament injury in a marking contest.

The defender ran back with the flight of the ball and tangled his legs with teammate Sean Dempster. He spent time on an exercise bike and doing short run-throughs before being put in cotton wool. 

"Robbo will miss a bit," Richardson said.  

"The early diagnosis – and I stress it is pretty early – would be that he'll miss a couple of weeks."