St Kilda skipper Jarryn Geary has been ruled out for the rest of the game against Richmond.
Geary collided with Richmond's Jack Riewoldt in the first term, going down to the rooms.
Triple M boundary rider Matt Thompson said it appeared the skipper has failed a concussion test.
"This is a big story for St Kilda, Jarryn Geary is putting his tracksuit on and taking his seat at the back of the bench," he reported.
"All we can presume from that is he's failed a concussion test and won't be back for the remainder of the day after that collision with Jack Riewoldt."
The defender was spotted on the bench early in the second term.