Uruguay suspended all football activity for the weekend on Friday due to "the delicate health situation of Juan Izquierdo", after the Nacional defender suffered an irregular heartbeat during the match against Sao Paulo in the Copa Libertadores.
Izquierdo, who replaced Sebastian Coates at halftime, fell to the ground unconscious in the 84th minute without coming into contact with another player.
Still unconscious, the 27-year-old was taken off the pitch in an ambulance. He is being treated at the intensive care unit of the Albert Einstein Hospital in Sao Paulo.
"Given the delicate health situation of footballer Juan Izquierdo, we inform our decision to suspend the professional football activity scheduled for this weekend," said the association for the rights of professional footballers in Uruguay, Mutual (MUFP).
"Our priority at the moment is to look after Juan's wellbeing, so we will closely follow his evolution in the coming hours," the association added.
Nacional posted on social media that Izquierdo is stable and remains sedated in the hospital's intensive care unit, where he will be "under observation for at least the next 72 hours".