Moussa Dembele fainted after a training session at Atletico Madrid on Tuesday, due to a reduction in blood pressure.
Having joined on loan from Lyon with a January purchase option, Dembele has only been with Atletico for a few months.
The incident happened at a preparation session, which included players who had not been called up for international duty.
The DirectoGol cameras caught Dembele keeling over and then crashing to the ground midway through the exercise.
Before seeking care, the 24-year-old was moved to the rehab role.
Later, the Frenchman was able to drive himself home later that day from the club’s training centre. He has since recovered.