Aaron Finch suffered a blow to his head during a Sheffield Shield encounter on Saturday and was substituted by Travis Dean after Australia's limited-overs captain experienced concussion symptoms.
Finch, who plays for Victoria, has been ruled out of the remainder of the match.
The 33-year-old Finch was fielding at short leg when he was hit on his helmet as New South Wales's Steve O'Keefe flicked a James Pattinson delivery during the second day's opening session.
Although Finch continued to field after being assessed, Cricket Victoria released a statement saying the right-hand batsman experienced delayed concussion symptoms during the lunch break.
"He was assessed on the ground immediately after the incident and was cleared to continue fielding, but experienced delayed concussion symptoms during the lunch break," Cricket Victoria said in a statement.
The incident comes on the heels of five-year death anniversary of Australian batsman Phil Hughes, who died from brain haemorrhage on November 27, 2014, after being hit on the neck by a rising ball while batting in a Sheffield Shield game in Sydney.
The Sheffield Shield has the concussion substitute rule in place since 2017-18 season. The rule was introduced in international cricket earlier this year.
Australia's Marnus Labuschagne was Test cricket's first replacement player when Steve Smith was concussed during the Ashes.