RICHMOND skipper Trent Cotchin is staring down the barrel of five weeks on the sidelines, with the club struggling for answers on how to halt his recurring hamstring injuries.

Cotchin, 31, suffered at least three hamstring strains in 2019 and another in 2020, with the most recent in the dying minutes of the club's important win over the Western Bulldogs last Friday night.

Coach Damien Hardwick said the club knew how and why the injuries were happening, but there were no easy solutions to the cause.

MEDICAL ROOM The full AFL injury list

"Our guys are very good medically at looking into the reasons why. It will be anywhere between three and five weeks (on the sidelines), we know that," Hardwick said.

"Sometimes these things just happen over a course of time, and he's had a really bad patch. We probably have a fair understanding as to why it's happening, but trying to get out of that mechanism is going to be tough. 

"He plays the game at such high intensity. The game is longer, the rotations are less – so we're putting him in at a more fatigued state – so the increased risk of injury is there, especially when you've had a predisposed history with that.

"The challenges are going to be there. Do we ask that player to slow down? You guys have seen Trent Cotchin play, he's not going to do that. These are the things that we need to continue to work through.

 "The game itself is challenging enough at 120 minutes with the limited rotations, and it's not necessarily the time they're spending on the ground, it's the [longer] time off the ground as well."

Along with Cotchin, the Tigers will lose integral defender Dylan Grimes (concussion) for Friday night's Grand Final rematch with Geelong, but are set to regain Nick Vlastuin (knee) superstar Dustin Martin from his own concussion bout.

Martin last week spent time in New Zealand visiting father Shane.

"He trained really well the other day, and sometimes a week off can freshen players up both physically and mentally," Hardwick said.

"So we think we'll get the very best version of Dusty this week, which is a good thing to have."

Hardwick confirmed last week's debutant Riley Collier-Dawkins will hold his spot.

"We were really impressed with how he went about it. He had 11 contested possessions on the night," he said. 

"We always knew Riley was going to probably be a better player at AFL level, which is really exciting for us. He's just got to build on that. 

"He's got some work to do on his game, but there's some strengths we really like in his game at the moment, so just got to make sure he continues to bring those."