Maxim Dadashev had never lost a professional boxing match when he entered the ring on Friday at the MGM National Harbor resort in Oxon Hill, Md.

But after 11 rounds in which his opponent, Subriel Matías, landed a series of heavy blows, Dadashev’s trainer urged him to accept defeat, eventually signaling to the referee that the match was over.

Dadashev, 28, collapsed as he was leaving the ring. He was then taken to the University of Maryland Prince George’s Hospital Center in Cheverly for brain surgery.

On Tuesday, he died from his injuries.

His wife, Elizaveta Apushkina, who lives in Russia with a young son, confirmed the death in a statement provided by the hospital. “He was a very kind person who fought until the very end,” she said. “Our son will continue to be raised to be a great man like his father.”