Zilisch, from North Carolina, sparked alarm among the crowd as he was initially motionless on the ground after a heavy blow to his head. Medics immediately arrived to tend to him and transported him on a stretcher to the trackside medical centre.

Nascar authorities said he was later transported to a local hospital for further evaluations but was awake and alert. Zilisch led 60 of the 82 laps to win Saturday’s Xfinity Series race.

He was released from hospital on Saturday evening and later wrote on social media: “Thank you everybody for reaching out today. I’m out of the hospital and getting better already. Thankfully, CT scans for my head are clear, I just have a broken collarbone.

“Thankful for all the medics for quick attention and grateful it wasn’t any worse.” 

Trackhouse Racing later announced that they would be withdrawing their No 87 Red Bull Chevrolet from Sunday’s Nascar Cup Series race. A statement read: “Trackhouse Racing has elected to withdraw the No 87 Red Bull Chevrolet from tomorrow’s NASCAR Cup Series race at Watkins Glen International. We wish Connor a speedy recovery”.