Barry McGuigan believes former world heavyweight champion David Haye would be wrong to step away from boxing.
Haye, 31 on Thursday, informed the British Boxing Board of Control he did not want to renew his licence.
"If it is the end then it's a shame because he had so much more to give," former world featherweight champion McGuigan told BBC Sport.
"As the Klitschkos showed, heavyweights blossom in their 30s. If it's the end then it's a career unfulfilled."
Haye's last fight was a defeat by Wladimir Klitschko in July when he lost his WBA world title by an unamimous points decision in Hamburg.
David Haye factfile
1980: Born in Bermondsey on October 13
2001: Loses to Cuban Odlanier Solis in the final of the World Amateur Championships in Belfast
2002: Wins first fight as a pro against Tony Booth
2004: Loses for the first time against former WBO champion Carl Thompson
2005: Beats Alexander Gurov for EBU cruiserweight belt
2007: Wins WBC cruiserweight title against Jean-Marc Mormeck
2008: Lifts WBO title against Enzo Maccarinelli and announces he's moving up to heavyweight
2009: Beats WBA heavyweight champion Nikolai Valuev on points
2010: Defends title against American John Ruiz in April
2011: Loses to Wladimir Klitschko in Hamburg in July
The Londoner had previously stated that he would not fight beyond the age of 30, but it was expected that he would hold off retirement
in order to fight Vitali
, the WBC champion and brother of Wladimir.
"It was a non-showing against Wladimir Klitschko. The tale about
his toe injury was embarrassing
and he boxed very timidly on the backfoot on the night," said McGuigan.
"Does he want to go out on that? I'm not sure. If it means making a big effort, training hard, fighting a couple of contenders and then facing Vitali or maybe Vladimir again, then he deserves that.
"His whole career has been full of bluff, so you don't know whether to believe the news."
Haye moved up from cruiserweight, a division where he was the unified champion, to heavyweight in 2008.
The Londoner beat Russian Nikolay Valuev to win the WBA title and twice retained the belt, beating John Ruiz and Audley Harrison, before losing his crown to Wladimir Klitschko.
"He was a very good cruiserweight and then won the heavyweight title but he was not convincing enough at that level," added McGuigan, 50, who beat Eusebio Pedroza to win the WBA featherweight belt in 1985.
Whether or not Haye confirms his decision to hang up his gloves, McGuigan believes British heavyweight boxing is in rude health.
"There's Tyson Fury, David Price and Anthony Joshua, who beat the Olympic and world champion at the world championships in Baku recently. The future looks very promising," he said.
"We would miss Haye, but the heavyweight division in Britain looks good."
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