CRUCIAL Richmond defender Dylan Grimes left training early on Saturday as doubt swirls over his availability for Sunday afternoon's blockbuster with ladder leader Brisbane as he battles an untimely right ankle issue.

The star stopper looked to be moving well but left the light session after 15 minutes, alongside captain Trent Cotchin (who hasn't played since round 19 and has been plagued by ongoing hamstring issues this season) and Dion Prestia.

Grimes spoke at length with fitness boss Peter Burge before leaving the track.

The Tigers withdrew midfielder Jack Ross from their emergencies list on Saturday, replacing him with defender Ryan Garthwaite.

That came after Ross trained on Saturday, despite the last session before a game usually being limited to those in the squad for the upcoming match.

Athletic tall Noah Balta worked alongside the defenders at Punt Road Oval.

Grimes was injured during the third term of last week's thrilling win over reigning premier West Coast but returned to the field for the final quarter.

Richmond would secure a spot in the top four with victory over the Lions at the MCG, leapfrogging Collingwood and potentially the Eagles as well, if they lose to Hawthorn.

The Tigers enter the clash with eight straight wins, a streak bettered by only Brisbane, which has won 10 on the trot.

Grimes, 28, has been integral to a defence that has been miserly since the bye, not having conceded more than 82 points since then, despite the absence of injured five-time All Australian Alex Rance.

He is ranked No.10 in the competition for total one percenters this season and No.13 for total intercepts.