Audley Harrison believes former heavyweight champion David Haye "has time to come back" to boxing.
Haye announced his retirement on Thursday - his 31st birthday - but had been linked with a fight with Vitali Klitschko in 2012.
Harrison's last fight was a comprehensive defeat to Haye last November and he plans to fight again.
Harrison told BBC Radio 5 live: "David is very young so he has definitely got time to come back and box again."
Haye's last fight was against Wladimir Klitschko on 2 July, when he lost his WBA title in Hamburg.
He now plans to pursue a career in acting after talks with Vitali Klitschko broke down.
Haye told BBC Sport this week: "Vitali is someone who would give me the opportunity to give me my credibility back.
"But that fight is not going to happen so you have to move on."
And Harrison - who is eight years older than Haye - does not expect to see Haye back in the ring against anyone other than one of the Klitschkos.
He added: "I thought David would carry on but it will be hard for him to fight anyone other than the Klitschkos now.
"He has gone to the top and to come back down and have a warm-up fight would be tough for him.
"But he goes off into the sunset and he has achieved a lot. A lot of boxers come back because of money problems but I don't think that will be a problem for David.
"He is very young so he has definitely got time to come back and box again if he wants to.
"He always had the goal of retiring at 31 but it wasn't the performance he wanted to retire on.
"That is why I am not retiring. I can't retire on my last performance [against Haye]."