BRISBANE and the Western Bulldogs have both been forced into activating their medical subs before half-time of Saturday night's semi-final. 

Jackson Payne, who was one of the Lions' three inclusions this week, suffered a cut head in a brutal collision with teammate Lincoln McCarthy and two Bulldog defenders. 

He spent several minutes on the ground before walking off with a large cut to his head. 

Ryan Lester was quickly subbed on, but the Lions were dealt another blow with Jarrod Berry also ruled out with a head knock. 

The Bulldogs also activated their sub at half-time with Jason Johannisen replacing Cody Weightman, who also suffered a head knock. 

Given all three injuries were head knocks it's likely to rule them out of the preliminary final as well. 

The Dogs will also be sweating on Marcus Bontempelli, who finished the game on the bench with a knee injury.