Friendly fire could be the reason for Ty Vickery’s bizarre AFL concussion incident.

Richmond have rested the ruck-forward for Saturday’s NAB Challenge match against Hawthorn in Beaconsfield.

Vickery started acting strangely in the first quarter of last week’s pre-season game against Fremantle, shaping for a marking contest even though the ball was well away from him.

Opponent Alex Silvagni alerted the Tigers to Vickery’s plight and he was helped off the ground.

As late as Thursday morning, Richmond were still mystified as to what caused Vickery’s scare.

They ruled out heat exhaustion and are sure it was related to a concussion.

Footage has since emerged of a glancing blow between Vickery and teammate Nathan Broad.

Vickery’s hands go to his head after the collision and minutes later he started showing signs of concussion.

Assistant coach Brendon Lade, who will coach the Tigers against Hawthorn, said they hope Vickery will be ready for their next pre-season match.

“It’s part of the game, it’s a contact sport and stuff like that happens,” Lade said.

“It’s quite disturbing, the vision, but Ty’s fine now – that’s the main thing.”

Lade said Richmond had been looking into whether Vickery was hit in the head during the warmup.

He added Vickery had undergone medical tests in the wake of the concussion.

“Our doctors, they put a lot of work into these kinds of areas,” he said.

“Whether it’s game day or the next game, we’ll do all the right stuff.

“We’ll make sure we get all the answers before we put him back out there and let him train again and play again.”

Fellow ruckman Ben Griffiths will also not play in Saturday’s game because of concussion.

Dockers opponent Aaron Sandilands caught him high with a block that sent Griffiths to the ground.

Sandilands was charged with rough conduct and will miss the first game of the season.

Richmond will field a much stronger side against Hawthorn, regaining captain Trent Cotchin, Dustin Martin, Jack Riewoldt and Alex Rance among others.

Brett Deledio is still a week away from resuming.

The Hawks will bring back premiership players Shaun Burgoyne, Cyril Rioli, James Frawley and Liam Shiels.

But Luke Hodge, Sam Mitchell, Luke Breust and Ben Stratton are among Hawks players who will not play.

Forward Jack Gunston also remains sidelined with a shin injury.