Shannon Briggs says he's heartbroken Wladimir Klitschko hung up his gloves ... 'cause he never got the chance to KICK THE LIVING HELL OUT OF HIM.
Briggs famously tormented Klitschko for years ... popping up on him in public places and trying to get Wlad to meet him in the ring (the paddle boarding ambush is still classic).
Klitschko just announced he's retiring, and when TMZ Sports talked with Briggs he told us he wishes the all-time great well -- that doesn't change the fact that he would've KNOCKED HIM OUT.
"I would've knocked him out cold! I'm sad, I'm sad he's gone, champ!"
Some things never change.
Klitschko announced his retirement from boxing on Thursday to scupper any hopes of a November rematch against Britain's Anthony Joshua.
Hamburg-based Klitschko, 41, hangs up his gloves as one of the all-time greats of the ring after a nine-and-a-half year reign as heavyweight champion, which was ended in 2015 and his last two fights ended in defeat.
He is behind only the great Joe Louis as the second-longest serving heavyweight champion of all time having enjoyed 18 consecutive defences over a nine-year span. Louis made 26 title defences between 1937 and 1949.
Klitschko, nicknamed 'Dr Steelhammer' due to the PhD he holds, won super-heavyweight gold at the 1996 Atlanta Olympic Games.
After turning professional, he was the undisputed world champion from 2006-2015, a period in which he held several belts.
His reign was ended two years ago when he finally lost to Britain's Tyson Fury on points.
Klitschko's last fight was in April when he was stopped by Joshua in the 11th round of the WBA, IBF, IBO title fight in front of 90,000 at Wembley Stadium in London in a hard-fought bout in which both fighters hit the canvas.