The 30-year-old, who has been capped five times for his country, collapsed to the turf with nobody around him during the second half of the Skybet Championship match at the Select Car Leasing Stadium.
Medical staff urgently tended to United midfielder Fleck for several minutes and he was momentarily brought back to his feet with an oxygen mask before being stretchered off to warm applause from both sets of supporters. He was substituted after 72 minutes and then taken to Royal Berkshire Hospital by ambulance. Sky Sports reported that he was conscious.
Sheffield United tweeted during the game: “Concerning moments as urgent medical attention needed for John Fleck. Play is yet to restart but the Scottish midfielder is on his feet and receiving further medical care.”
They then posted: “John Fleck leaves the field on a stretcher after receiving urgent medical care. Our thoughts are with you, Flecky.”
Sheffield United went on to win the match 1-0, with the club offering an update at full time. “3 points for the Blades,” they wrote. “More importantly, John Fleck was conscious when he left the stadium via the ambulance gate. We’ll provide supporters with a further update once known. Get well soon, John.”
When asked about Fleck’s condition in his post-match interview, Sheffield United manager Slavisa Jokanovic said: “He’s in hospital, he’s conscious and he’s asked for the result. We hope everything will be ok.
"He is safe, in good hands and we pray that everything will be okay.”