Kessler's career intertwined with Froch and Calzaghe's. He became world champion in 2004 and unified the division. In 2007, he lost to Calzaghe by unanimous decision. Three years later, he beat Froch the same way. Froch got his revenge in 2013, which turned out to be Kessler's last pro fight.
The Dane is one of the few fighters who faced both Brits, giving him a unique perspective on their hypothetical clash. He broke down their styles for The Daily Mail.
"It is difficult to say who is best. Joe was not a puncher – he was fast but he was hitting with the inside of his glove but he got the points when they landed. He was mentally strong. He was in very good shape all the time."
Kessler painted a picture of Calzaghe as a speedy, mentally tough fighter who was always in top form. He didn't hit hard, but his punches scored points.
On the other hand, Kessler described Froch's style:
"Carl is more of a fighter and throws lots of punches one after the other. He wants to trade punches. If Carl was in there throwing his big punches and his uppercuts then he would have hurt Joe."
'The Cobra' Froch liked to trade blows and throw combinations. His power could have caused Calzaghe problems.
Despite Froch's punching power, Kessler leaned towards Calzaghe as the likely winner.
"Who would win out of those two? I would think Calzaghe. Maybe."
Kessler's not the only one weighing in on this fantasy fight. Chris Eubank Sr, who once fought Calzaghe, has also shared his thoughts on who would come out on top.
The Froch-Calzaghe rivalry never made it to the ring, leaving fans to wonder what might have been. Kessler's insight gives a glimpse into how this dream match could have played out.