Boxing legend Mike Tyson says he is convinced there is more to come from British heavyweight David Haye.
Haye retired after losing on points to Wladimir Klitschko in July 2011 but returned to the ring to stop Dereck Chisora this summer and is now pursuing a fight with Klitschko's brother Vitali.
And Tyson, a former undisputed world heavyweight champion himself, told Sky Sports News: "David should continue to fight because he's a young guy.
"I thought David fought very well against Klitschko and I have a lot of respect for him because I expected him to be obliterated.
"Unless he has something else to do and plenty of money he should definitely keep fighting because he can get better and better.
"Fighting is our profession and it's what we do. I fought 15 times one year."
Tyson has also welcomed the decision of Ricky Hatton to return to the ring later this year, saying: "He's a young guy and, if that's what he wants to do, he should carry on.
"If he can take the beating (Manny) Pacquiao gave him and become a champion again, that's what boxing is all about.
"Fighting is a metaphor for life. It's about endurance and proving how much you can take."
The current heavyweight scene is seen by some as colourless because of the domination of the Klitschko brothers.
But Tyson is full of praise for the duo and said: "They should dominate. They have learnt their craft and overcome adversity.
"People want to see very exciting guys, talking smack and knocking guys out. People want barbarism and blood.
"But I love what the Klitschkos are doing. They beat people, they inspire people and they're erudite, they show you don't have to be brainless to be a boxer."
Asked if he would have defeated the brothers in his prime, Tyson added: "I'd like to think so, my ego makes me think so! But these guys would have been hard to beat in any era, they're changing the face of boxing."