Leeds United's Jack Clarke was taken to hospital after he began to feel ill during the second half of the game with Middlesborough.
The 18 year old winger had received medical attention on the bench.
He has gone to hospital with the club's head of medicine and performance
Leeds United manager Marcelo Bielsa said: "What we know is that he didn't feel well, We don't really know the reasons yet.
"After feeling bad he recovered and when he was taken to the dressing room he was better, as if he had overcome the problem. He was taken to the hospital to see if everything was alright."
Leeds United have issued this statement on their website.
"Jack Clarke began to feel unwell during the second half of our Sky Bet Championship fixture with Middlesbrough and received medical attention.
The player is responsive and attending hospital with the club’s head of medicine and performance.
On behalf of everyone at Leeds United, we would like to thank the medical staff from both clubs for their response to the incident."