US boxer Day 'extremely critical' after devastating knockout

Los Angeles - American boxer Patrick Day was fighting for his life in critical condition in hospital on Sunday night after lapsing into a coma following a vicious knockout by Charles Conwell the night before.

The 27-year-old Day suffered a "traumatic injury" and underwent emergency brain surgery on Saturday night after being knocked out by Conwell in a super welterweight bout on the card at Chicago's Winstrust Arena.

"Patrick is in a coma caused by the injury and is in extremely critical condition," said fight promoter Lou DiBella. "We appreciate the outpouring of support, prayers and offers of assistance from all corners of the boxing community."

Day is in intensive care in Northwestern Memorial hospital. No specific details of Day's injuries were provided by the promoter.

Conwell asked his social media followers to pray for Day's recovery. "Keep him in your prayers!! #prayforpatrickday," he wrote on his Twitter page.

"Pat Day makes any room he is in a better place. Never saw him greet someone without a big smile," DiBella wrote on Twitter. "Life doesn't seem fair sometimes. Please keep Pat in your prayers, thoughts and hearts."

Day was unconscious when he was taken from the ring in a stretcher and loaded onto a waiting ambulance. He suffered a seizure in the ambulance and needed a breathing tube once he arrived at the hospital.

Conwell, a 2016 American Olympian, was dominating the fight dropping Day in the fourth and eighth rounds and then landing a right hand in the 10th which caused Day to stumble.

Seconds later he rocked Day with a massive left hook that resulted in Day falling backwards and his head bouncing off the canvas. Referee Celestino Ruiz called off the fight at one minute, 46 seconds of the round.

Day lay on the canvas for several minutes while receiving medical treatment before being removed from the ring.

Day was coming off a loss in June to Carlos Adames in New York. He has 17 wins and four losses and one draw in his pro career which began in 2013.

Day was fighting on the undercard of Russian Dmitry Bivol's successful World Boxing Association light-heavyweight world title defence over Lenin Castillo.