Leeds’ teenage winger Jack Clarke was taken to hospital after complaining of feeling unwell during Saturday’s Championship draw at Middlesbrough.
The 18-year-old, who started the match and was replaced at half-time, was treated by paramedics and carried away from the substitutes’ bench on a stretcher.
Leeds boss Marcelo Bielsa confirmed Clarke was feeling “better” in the dressing room but would be checked in hospital.
Bielsa told BBC Radio Leeds: “What we know is that he didn’t feel well. We don’t really know the reasons yet.
“When he was taken to the dressing room, he was better. He was taken to the hospital to see if everything is all right.”
The second-half incident at the Riverside Stadium caused a significant delay to play and 12 minutes injury-time was added on.
Kalvin Phillips scored a 101st-minute equaliser to secure a 1-1 draw that took Leeds top of the Championship.