Abel Sanchez knows weight classes are there for a reason. And he maintains that, unfortunately for Terence Crawford, he’ll find out hard way.

After poking and prodding Canelo Alvarez for months, Crawford (41-0, 31 KOs) got what he was looking for — a matchup with the Mexican star Sept. 13 at Allegiant Stadium in Las Vegas, Nevada.

Alvarez fights two divisions north. But desperate to prove that he’s the better fighter, Crawford, who had only one fight at 154 last year after fighting at 147 since 2018, agreed to jump to 168.

The Ring’s No. 3 pound-for-pounder likes his chances, but Sanchez, a longtime trainer who knows Alvarez well, doesn’t.

Sanchez, who led Gennadiy Golovkin in two fights with Alvarez that ended in a split draw and majority decision defeat, also saw light heavyweight champion Dmitry Bivol fail to significantly hurt him in 2022.

"Terence Crawford is a great fighter, but that's why we have weight divisions. Canelo has proven as he's risen in weights, he's dealt with the best in his weight division," Sanchez, who is working the corner of heavyweight Filip Hgrovic for Saturday's bout vs. David Adeleye on DAZN PPV, told The Ring's Louis Hart. "He fought Bivol and Bivol couldn't hurt him. He fought my guy and my guy couldn't hurt him in two fights."

Crawford, 37, hasn’t exactly come close to losing. He picked up the WBA junior middleweight title against Israil Madrimov last year in Los Angeles, California. Aggregating every 154-pound belt was feasible, but no one in that division could match the payday or credibility that Alvarez could bring.

For a while, Alvarez (63-2-2, 39 KOs) didn’t entertain it. Once the call-outs and money became too much to ignore, he gave Crawford his full attention after beating William Scull.

Alvarez did just enough to overcome Scull, who refused to stand still, on points May 3 in Riyadh, Saudi Arabia, to become a two-time undisputed super middleweight champion.

Alvarez didn't look great, but Sanchez has seen enough to be confident in his assessment. Not too long ago, Crawford was a junior welterweight (140). Alvarez turned pro at that weight class in 2005.

"If he had taken three or four years ike Canelo did and built up not only his strength but his bulk in a correct way, he would've had a better chance," Sanchez said. "To do it in the 14, 15 months he's done it in, it's going to be tough. ...

"Crawford is going to be a lot slower because of the weight also. Once [Canelo gets his timing down] I think it'll be a sparring session for Canelo as it is in most of his last four or five fights. After the fifth or sixth round, it seems like a sparring session. He's doing whatever he wants."