Saints defender Dylan Roberton is still recovering in the Epworth Hospital in Geelong after collapsing in Sunday's clash against the Cats.
The Saint was lining up on the centre square in the second quarter, as the ball was getting tossed up in the middle and collapsed to the ground. There was no contact, and no one within the near vicinity as he fell to the ground. Precautionary measures were taken immediately, with doctors accompanying the defender to the rooms, where he was later taken to the hospital.
The initial diagnosis was an arrhythmia, which is an irregular heart beat.
St Kilda Football Manager Simon Lethlean spoke to RSN radio on Monday morning about the incident, and said Roberton was in good spirits at the hosptial.
"Last conversation we had last night he was feeling OK, feeling alert, eating a meal," Lethlean told RSN on Monday.
"He's having a number of tests and we'll get an update this morning but we're taking it quite seriously, as you can imagine.
"It's nothing that has been historical for him, I think the doctors described it as an irregularity in the heartbeat but it's just the on the spot diagnosis from what Dylan said he felt faint and dizzy and just blacked out.
"He then had some test and they noticed some irregularity in his pulse."
Lethlean confirmed it would be a "surprise" if Roberton took to the field this weekend following the incident.