West Coast chief executive Trevor Nisbett has expressed his concern over the welfare of star on-baller Ben Cousins following the death of club legend Chris Mainwaring.

Mainwaring, who died of a heart attack in the early hours of Monday morning, shared a close bond with Cousins and helped convince the 29-year-old to enter drug rehabilitation earlier this year.

Cousins twice rushed to the aid of Mainwaring on the day of his death, bringing him food on the second occasion before leaving at about 10pm on Sunday night.

Less than three hours later, the 41-year-old was found unconscious by police and ambulance officers at his Cottesloe home and rushed to hospital.

Nisbett said he was concerned that Cousins, who spent a month in a US drug rehabilitation clinic in April, might relapse.

"We were concerned about him (Cousins) yesterday. He was with his dad trying to come to terms with what had happened to a friend that had helped him," Nisbett said.

"We are very concerned about Ben and we'll continue to be concerned until Ben can categorically say he's rehabilitated completely."

"He knows he's not out of the woods. He's got a long way to go yet, and he's working so hard at that and we are extremely proud of him at the moment."

"There's been a lot of rumour and innuendo about Ben since the footy's finished and he's in great shape. He's been doing everything we've asked of him. He'll hopefully continue to do that."

Nisbett praised Mainwaring for his role in convincing Cousins to enter drug rehabilitation.

"What it says is Chris may have experienced it in a former life and consequently he was trying to help a friend at the start of the year," Nisbett said.

"He knew the dangers and he was trying to assist Ben with getting him to rehab, which is often tough when people don't recognise they've got a major problem."

"That's what Mainy did for us. And when he was going through some personal problems just recently Ben was trying to return the favour."

Nisbett slammed Melbourne radio commentator Neil Mitchell, who suggested Mainwaring's alleged use of cannabis and ecstasy on the night of his death was an extension of West Coast's own drug troubles.

"Well that's Neil Mitchell," Nisbett said bluntly.

"Neil's been on our case for a number of years. He obviously has no empathy for what's happened, which is very disappointing, but that's his opinion."

"We recognised late last year the problems we had within our club with the current group of players and I think Chris' situation is an entirely different thing."