Paceman Joe Mennie has been diagnosed with a small skull fracture and brain bleeding after being struck on the head during training with the Sydney Sixers.
Mennie, who made his Test debut for Australia last November, was hit in the nets with a ball by Sixers team-mate and batsman Michael Lumb on Monday ahead of Wednesday's Big Bash League semi-final against the Brisbane Heat.
The 28-year-old was taken to hospital and later released, however, scans have revealed a serious head injury, with Mennie readmitted to hospital as a precaution.
"After being struck on the head by a ball at training on Monday, Joe was transported to a hospital in Brisbane where he underwent a series of check-ups before being discharged later that evening," Cricket Australia Chief Medical Officer, Dr John Orchard said.
"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. Whilst this is a serious injury, Joe is feeling well. We believe that this is a stable injury and will not require surgery.
"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, who was part of Australia's humiliating defeat to South Africa in Hobart, has claimed two wickets in two appearances for the Sixers.