Collingwood are concerned about defender Ben Sinclair's health after his fourth concussion this AFL season.
Sinclair was taken to hospital as a precaution after he was knocked out in a collision with Jed Anderson during Friday night's loss to North Melbourne.
Magpies coach Nathan Buckley said on Monday night that Sinclair would not play this Saturday against West Coast.
"We are really concerned about `Sinks' and his long-term future in the game," Buckley told AFL360.
Buckley compared Sinclair to Hawthorn star Cyril Rioli, whose running style was overhauled successfully after a number of serious hamstring injuries.
"The way that Cyril Rioli had to learn to run again, we might need to teach `Sinks' to moderate his attack on the ball and the man," Buckley said.
"He's a cannonball when he goes."
Buckley said Sinclair could play again this season.
He added that tests did not suggest that Sinclair's concussion issues were as serious as the problems that forced Brisbane defender Justin Clarke to retire earlier this season.
"All the tests that Ben has had don't suggest anything to that level, but at the same time, he's only just coming into his own," Buckley said.
"From a football standpoint, it would be great to see him have the opportunity to explore this confidence he's found and the belief in himself.
"He's been one of our better performers in the last month.
"But I tell you what, it doesn't matter ... his long-term health is the absolute priority."
Sinclair, 24, has played 63 games since his 2011 senior debut.