PAUL Roos won't put a number on how many Melbourne players could be facing the axe at season's end, but says those that are shouldn't be surprised when they get the bad news.

After almost a season and a half at the helm of the Demons, Roos has conceded some players still aren't "buying in" to his game-plan.

The Melbourne coach said he was happy with his team's top performers, but remained concerned about the lower tier of players.

However, he was reluctant to put a number on how many changes may be required.

"It changes dramatically," he said at AAMI Park after training on Thursday. 

"It's about identifying players that can do what coaches want," he said.

"That us-versus-them mentality, that's 30 years ago.

"Now it's about a collective group, coaches and players working really hard together to get an end result.

"And we've seen it – if coaches can't do it they go, and if players can't do it they go.

"It's a pretty black and white system."

Roos said he was in constant dialogue with his players, but hadn't felt the need to directly tell any just how high the stakes were. 

"They would know that, it's not something that needs to be dramatised," Roos said.  

"I don't sit there and say to a guy, you're playing for your career," he said.  

"But players are smart enough to understand through the discussions you have, and where we want to go as a footy club, that if they don't keep up with what we want to do, someone is going to jump over the top of them." 

Roos said ruckman Mark Jamar would need to find some form in the VFL before earning a recall to the senior side, having lost his spot primarily because of a concussion. 

Dom Tyson (knee) should be right to play against Collingwood on Queen's Birthday after competing all over training on Thursday.