LAS VEGAS – This will be the last time Errol Spence Jr. squeezes his body down to 147 pounds.

Spence informed BoxingScene.com before he made an appearance at open workouts Wednesday at MGM Grand that his next fight will be contested at the junior middleweight limit of 154 pounds. The 33-year-old Spence will oppose fellow undefeated welterweight champion Terence Crawford in their highly anticipated 147-pound title unification fight Saturday night at T-Mobile Arena.

They have rematch clauses in their contracts, but Spence doesn’t think he can put his body through the grueling process of making the welterweight limit again.

“I would want it at 154,” Spence said. “I’ve outgrown 147.”

The weight limit for their rematch will be determined by the winner, however, thus Spence (28-0, 22 KOs) could be forced to fight Crawford (39-0, 30 KOs) at welterweight again if Crawford wins and wants their second bout to be contested at 147 pounds as well. Spence would then have to decide if avenging what would be his first professional defeat would be meaningful enough to make the physical sacrifices required to fight at welterweight again.

Spence nevertheless acknowledged a little less than two days before he has to make weight Friday that the process is increasingly difficult, even with top professionals helping his cause every step of the way during training camp.

“It’s been kinda hard,” Spence said, “but I’ve got a nutritionist and a dietician to make sure I’m eating the right foods and make sure I’m good. But it’s definitely hard. It’s definitely a struggle. It’s always hard, but yeah, this is the last time, definitely. I’m a lot older. I’m not as young as I used to be, so you know, you can’t be puttin’ your body through that much to fight.”

Except for one fight, the 5-foot-10 Spence has fought at or near the welterweight maximum of 147 pounds since he turned pro after the 2012 Summer Olympics in London. The DeSoto, Texas native has come in at or below 147 pounds for each of his last 10 fights, the last seven of which were championship clashes.

The 5-foot-8 Crawford, meanwhile, will participate in his eighth straight welterweight fight Saturday night. The Omaha, Nebraska native has won each of his seven 147-pound bouts by knockout or technical knockout since the former undisputed 140-pound champion moved up seven pounds five years ago.

MGM Grand’s sportsbook listed Crawford as a slight favorite Wednesday to defeat Spence (-160/+135). Crawford or Spence can become boxing’s first fully unified welterweight champion of the four-belt era by winning their Showtime Pay-Per-View main event ($84.99; 8 p.m. EDT; 5 p.m. PDT).

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