Kessler, Froch, and Calzaghe were the standout super middleweights of the 2000s. They all competed at 168lbs and left their mark on the division in different ways.
Calzaghe ended his career unbeaten with 46 wins. He held the WBO belt for over a decade and made 20 title defenses, becoming the longest-reigning 168lbs champion.
Froch's career also shone brightly. He beat Kessler, Jean Pascal, and Lucian Bute. His final fight at Wembley Stadium drew over 80,000 fans to see him beat George Groves for the second time.
Kessler himself had an impressive 46 wins in 49 fights. He became a unified world champion at 168lbs, lost to Calzaghe in 2007, beat Froch in 2010, and ended his career with a rematch against the Nottingham fighter.
When asked about a hypothetical Froch-Calzaghe matchup, Kessler said:
"Who would win out of those two? I would think Calzaghe. Maybe."
Kessler broke down both fighters' styles. He described Calzaghe as fast and mentally strong, always in good shape. Calzaghe wasn't known for his punching power but scored points by hitting with the inside of his glove.
Froch, on the other hand, was more of a fighter. He threw lots of punches in succession and liked to trade blows. Kessler noted that Froch's big punches and uppercuts could have hurt Calzaghe.
The debate about how a Froch-Calzaghe fight would have played out continues to this day. Frank Warren, Calzaghe's promoter, is certain his fighter would have won.
Froch's career achievements, including victories over Kessler, Pascal, and Bute, have cemented his place in boxing history. But the question of how he would have fared against Calzaghe remains one of boxing's great "what ifs".