Former world champion Barry McGuigan has insisted there are no doubts over the courage of Amir Khan following his defeat by Terence Crawford.
Saturday's WBO welterweight title fight ended in controversial fashion when champion Crawford, who had knocked Khan down in the first round, won with a sixth-round stoppage after his British opponent was unable to continue following an illegal low blow.
The American, who had been on top for much of the bout, accused Khan of quitting but the beaten fighter was adamant he could not continue.
McGuigan, 58, who won the world featherweight title in 1985, gave his support to Khan by telling BBC Radio on Sunday: "It's a very dangerous thing to do to call somebody a quitter.
"You look at Khan's career and the fights he's been in and the one thing he always had was immense courage, determination and getting up off the floor.
"You think of the Breidis Prescott fight, the Canelo (Alvarez) fight, the Danny Garcia fight -- there's no quit in him."
Khan meanwhile continued to insist Sunday he had been left with little option but to stop boxing when he tweeted he had been urinating blood.
He tweeted: "Peeing blood. The shot was low. The fight was just getting interesting. Well done team Terrance. I never quit, I rather get knocked out cold then quit. Good night. Thank you New York."