St Kilda's Dylan Roberton has been taken to hospital for tests on an irregular heartbeat after his frightening collapse during the Saints' 47-point loss to Geelong.
Roberton fell to the Kardinia Park turf without contact during the second quarter of the Cats' 15.13 (103) to 7.14 (56) AFL win on Sunday.
He lined up outside the centre square after a Geelong goal and fell to the ground as he jogged into the square after the bounce.
He was able to get to his feet after about 30 seconds, walked from the ground unaided and was taken to Geelong's Epworth Hospital.
"It looks like some sort of irregular heartbeat ... (but) from all reports he's alert and he's eating," coach Alan Richardson said.
"He's doing well but it's obviously a bit of a shock. He shocked a few of his mates but he's doing well, which is positive.
"I've never really seen anything like that so my thoughts were immediately with (him).
"But it was really comforting to get some feedback that he's OK now."
St Kilda were left with two fit players on the bench in the second half after ruckman Rowan Marshall was ruled out with concussion.
Richardson refused to excuse the poor performance despite the casualties.
The Saints slipped to a 1-3 record and have lost their past three games by an average margin of 49 points.
"We were beaten pretty badly by the Cats ... their physicality and their pressure was just too much for us and that's disappointing," the coach said.
"We've got too many (players) out of form, there's no doubt about that."
Geelong also lost Cory Gregson to a foot injury in the first half.
It was a welcome return to the winners' list for the Cats after two losses.
"We got the game on our terms early," coach Chris Scott said.
"They didn't take their chances so it wasn't like we were completely dominating but the game was being played the way that we tried to set it up."
Tom Hawkins was held goalless by Nathan Brown but Daniel Menzel finished with a game-high five goals.
With injured superstar Gary Ablett looking on, youngster Brandan Parfitt stepped up with an eye-catching 28-possession, three-goal game.
Making his 143rd appearance as skipper, Joel Selwood overtook Cats legend Reg Hickey to become the club's longest-serving captain.
He celebrated the milestone with 27 disposals in an influential display.
Luke Dunstan, Jarryn Geary and Jack Steven each had 26 possessions for the Saints.