Sunderland manager David Moyes says Patrick van Aanholt was withdrawn from Sunday's game against Tottenham after the club received the results of a standard cardiology scan.
The results are believed to have been given to Sunderland by an independent expert cardiologist, who also works for the Football Association Consensus Panel, at 3.50pm for the 4.30 kick-off and they were advised not to play him. The club then decided to withdraw the player.
The FA had no involvement in the player's referral, the screening process or the communication of the results with the club.
Moyes explained Van Aanholt's withdrawal at his press conference ahead of Wednesday's EFL Cup game at QPR.
Moyes said: "He had the statutory checks with the cardiologists and the FA panel of cardiologists looked at it and advised us really late on Sunday that he should not play until further tests had taken place.
"They gave us the results at 10 to 4 when the player was warming up and we had to make a decision on the spot."
While Moyes had no hesitation in taking the action he did for the benefit of both the player and the club, he was concerned at the late notification of a potential issue.
He added: "We are just surprised that the FA panel didn't contact me or contact my doctor until 3.50pm on Sunday afternoon. I have never in my career been put in a situation like that ever, so we had that to deal with.
"We just can't understand why the message would come to us at that time, 30 minutes before the kick-off.
"It was completely outside our control, but it was in our control because we knew we had to make the correct decision for the player and for the football club. We had to do that."
An FA spokesperson confirmed to Sky Sports News HQ that the governing body, which carries out around 1,400 screens across England and Wales each year, had no formal involvement in the Dutchman's cardiac screen.
The spokesperson said: "This cardiac screen was not conducted as part of The FA's cardiac screening programme, therefore, The FA had no involvement in the player's referral, the screening process or the communication of the results with the club.
"On occasion, clubs may seek independent advice on a player's cardiac health from an expert cardiologist who sits on The FA Consensus Panel, which is an expert body in this area.
"Cardiologists who sit on The FA Consensus Panel are hugely respected and vastly experienced specialists who place the patient at the very centre of their care and their only concern will be in regard to the wellbeing of that individual."
Van Aanholt has now had further tests and has been given the all-clear to play again. He will travel to London with the rest of the squad for the EFL Cup third-round clash with QPR at Loftus Road, although Moyes is yet to make a decision on whether or not he will be involved.
The Scot, who is happy that the player has recovered mentally from a worrying experience, said: "He's had some further tests and will travel to London with us, and we will make a decision on that a little bit later."