Jermell Charlo has sparred plenty of rounds against heavier opponents who couldn’t hurt him.

There is quite a difference, Charlo conceded, to sparring sessions that provide protection in the form of headgear and gloves with more padding and actual boxing matches. That’s why Charlo admitted during a recent interview with Showtime’s Brian Custer that he won’t have a real feel for the difference between taking punches in the 154-pound and 168-pound divisions until the bell rings to start his super middleweight title fight against Canelo Alvarez on September 30 at T-Mobile Arena in Las Vegas.

“Truthfully, I won’t really know until I actually get in there with the 10-ounce gloves,” Charlo told Custer for an episode of Custer’s “The Last Stand” podcast. “Like I won’t know because of the fact that the power in the punches could be a little bit different with a 10-ounce glove. But I’ve been in the ring with a lotta guys that’s like way bigger than Canelo, way bigger than me, and that’s because of the fact that, you know, I was knocking guys out in sparring.

“And so in order to spar with a 54-pounder, a lotta them would have to gain a lotta weight. You know, I could feel it and I could feel like when someone was a little too heavy, but that time should rewind itself now and bring itself back because this is what Imma be facing.”

The 6-foot Charlo’s chin has been one of his greatest strengths throughout the undisputed 154-pound champion’s career. Except for one fight, the Houston native has competed at or near the junior middleweight limit of 154 pounds for the past 13 years, though, whereas the 5-foot-8 Alvarez has displayed a granite chin and power while the former 154-pound champion succeeded in the 160-pound, 168-pound and 175-pound divisions.

The 33-year-old Charlo has not competed at the middleweight maximum of 160 pounds during his 15-year professional career, yet that didn’t stop the IBF/WBA/WBC/WBO 154-pound champion from moving up two weight classes, 14 pounds altogether, to challenge Alvarez in a Showtime Pay-Per-View main event. Alvarez, also 33, is 7-0, including four knockouts, in super middleweight fights and has been that division’s fully unified champion since he knocked out then-unbeaten IBF champ Caleb Plant in the 11th round of their November 2021 bout at MGM Grand Garden Arena in Las Vegas.

Mexico’s Alvarez (59-2-2, 39 KOs) is thus listed as a 4-1 favorite by most oddsmakers to beat Charlo (35-1-1, 19 KOs) in their 12-round fight for Alvarez’s IBF, WBA, WBC and WBO 168-pound championships.

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.