Australian paceman Joe Mennie suffered a "minor brain bleed" and fractured skull after a ball hit his head during training, Cricket Australia (CA) said Wednesday.

Mennie was bowling at a nets session with his Twenty20 Big Bash League team the Sydney Sixers in Brisbane on Monday when a ball struck the side of his head.

CA chief medical officer John Orchard said Mennie was initially discharged from hospital that night but follow-up scans the next day revealed his injures were worse than first thought.

"Joe was reviewed by a Cricket Australia doctor on Tuesday and had some scans performed that revealed a small fracture and associated minor brain bleed," Orchard said in a statement.

The medic described the injury as serious but said Mennie was "feeling well".

"We believe that this is a stable injury and will not require surgery," he added.

"As a precautionary measure, Joe has been admitted to hospital for observation and will continue to be assessed by a neurosurgeon to determine best course of action."

Mennie was released from hospital later Wednesday and was cleared to fly out from Brisbane with his team on Thursday, the Sydney Morning Herald reported.

The Sixers are due to take on the Brisbane Heat in the BBL semi-final on Wednesday night.

The newspaper said he would not play in the semis and would be monitored over the next few days.