St Kilda's rucking stocks got even thinner with Trent Knobel to miss the remainder of the AFL season with a serious neck injury.

Knobel will be out of action for at least 12 weeks after being concussed when landing heavily in a ruck contest during the five-point win over Brisbane at Telstra Dome on Saturday night.

Further tests revealed he had suffered damage to the number one vertebra, forcing him to spend the next six weeks in a neck brace.

Young ruckman Barry Brooks also suffered a season-ending knee injury last weekend while playing for the Saints' VFL affiliate Springvale.

Knobel's enforced absence makes the Saints' decision to sack two-time Kangaroos premiership ruckman Matthew Capuano last month even more contentious.

But coach Grant Thomas pledged that there would be no about-turn on the Capuano dumping.

"We never go back," he said.

"We made that decision based on what we decided at that point in time and we have no regrets about that whatsoever."

Knobel said he was wearing the brace because the vertebra had moved.

"Over time it will heal itself, but 12 weeks is the worst-case scenario," Knobel said.

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