Kildare defender Emmet Bolton suffered concussion during the third quarter of Ireland's International Rules Test win against Australia earlier today.
Bolton came off second best in a collision with powerful Australian forward Mitch Robinson, as the players competed for a loose ball in the Irish defence.
As Robinson rolled over the top of a grounded Bolton, the Eadestown clubman sustained a blow to the neck and head area and received immediate medical treatment.
He was stretchered off and is viewed as a major doubt for the second Test on the Gold Coast next Friday. Donegal's Karl Lacey is the likely replacement.
Speaking after the 80-36 success in Melbourne, Ireland manager Anthony Tohill said: "Emmet has taken a fairly heavy hit to the head.
"It was a big hit but he's a tough lad. He is probably a big risk for next week."