PREMIERSHIP defender Jake Lever has sent a scare through the Melbourne camp after fainting during a pre-season session on Monday.

It was the Demons' first official return to training and the full list took part in a gruelling running session under the guidance of new high performance chief Selwyn Griffith.

On a warm Melbourne day, the players were spared no favours from the sun, and a number of them fell to their haunches following the running drills.

However, the No.1 concern was with the 25yo Lever, who fainted on the far side of Casey’s ground and had medical staff huddled over him for 15 minutes. 

He was responsive as medical staff asked questions, with both coach Simon Goodwin and head of football Alan Richardson checking on his wellbeing. 

Lever was finally able to return to his feet after a lengthy period, walking unassisted and leaving the track. A club spokesman said he just went a bit too hard, too early. 

The club said Lever was fine and, after he was assessed, he was sent home to rest.

Griffith has taken over the top role after serving under renowned fitness guru Darren Burgess, who left for Adelaide. He has already had the Demons' flag stars working hard over their off-season breaks.

Ahead of the session on Sunday, midfielder Jack Viney said: "He [Griffith] wants to make his mark pretty early and he's got us training really hard at the moment. There's a bit of nervous energy about the (1km) time trials."

Viney, 27, who is entering his 10th pre-season program, said the sheer number of players at unofficial training sessions during the break was a good sign.

"It has allowed us to train to a really high quality and even get some low-level drills and game simulation happening," Viney said.

"From personal experience, I think the majority of the playing group are even fitter than they were coming into the pre-season last year."