Richmond defender Graham Polak could be left with long-term brain damage after the AFL player was hit by tram while walking with teammates.

The 24-year-old is in an induced coma in hospital after he suffered bruising to the brain in the accident late last night following his team's loss to Carlton in a match at the MCG celebrating Richmond's centenary.

Polak's ongoing health, and his AFL career, remain in limbo and the next few days will be critical for his long-term prognosis, doctors said.

His mother and three brothers flew from Perth today to be at his bedside in Melbourne's The Alfred Hospital, along with his partner Alyce.

"Graham has suffered bruising to the brain and is being kept in a medically induced coma," the Richmond club said in a statement.

"At the moment Graham's condition is expected to remain unchanged throughout the night ... there will be no further comment from the club until tomorrow."

Polak was crossing the intersection of Orrong and Dandenong roads in suburban Armadale around 11pm (AEST) when he was hit.

Team mates Cleve Hughes and Jordan McMahon were with Polak at the time.

Ambulance officers had to work on the unconscious Polak, and were forced to insert a tube to assist his breathing, before he was rushed to hospital.

Club doctor Greg Hickey said Polak had been moving his limbs, but it was too early to say whether there was any long-term brain damage.

"Probably the hardest thing to gauge at this stage is more his intellectual recovery, whether he will regain that - time will tell," he said.

"Long term, it's very hard to say - these things can take some months to settle down and get a clearer picture of where he's at.

"In terms of footy, it is unquestionable he won't play this season, longer term beyond that, we'll just have to wait and see."

Hickey had initially expressed optimism that Polak might come out of the coma sometime today but plans were changed.

"He's going to be in hospital for some time ... whether he will need a period of rehabilitation after that in some sort of other facility, I'm not sure," Hickey said.

"Things are going to change very quickly over the next few days."

Tiger veteran Matthew Richardson described the news as "a shock".

Richmond football director Greg Miller said Polak's teammates had been told of the accident last night.

He also said it was unclear if alcohol played a role in the accident.

"I'm unaware of that, it's not a concern for us at the moment," Miller said.

Polak has played 11 games for Richmond this season for a career total of 106.

He joined Richmond from Fremantle in late 2006 and last year finished seventh in the Tigers' best-and-fairest award.

AAP