LAS VEGAS – Canelo Alvarez and Caleb Plant were kept apart again after they weighed in Friday afternoon at MGM Grand Garden Arena.

Fearful of another brawl on stage, organizers of their Showtime Pay-Per-View main event separated the super middleweight champions from the time they arrived until the time they left. They jawed at each other from several feet away, with promoter Tom Brown, event security and even Mike Tyson between them.

They were extra cautious because Alvarez and Plant came to blows during their first press conference September 21 in Beverly Hills, California. Alvarez opened a scrape beneath Plant’s right eye during that skirmish, when he punched Plant’s sunglasses into his skin.

Six weeks later, a loud crowd at a weigh-in that was open to the public cheered Alvarez wildly and chanted his nickname when he arrived, when he got on the scale and when he again thanked them for coming from the front of the stage.

Alvarez, 31, officially weighed 168 pounds when he stepped on the Nevada State Athletic Commission’s scale for their 12-round super middleweight title unification fight Saturday night. Plant, 29, came in at 167 pounds.

They’ll fight for Alvarez’s WBA, WBC and WBO belts and Plant’s IBF crown. Short of a draw or a no-contest, the winner will become just the sixth fully unified champion in any division during boxing’s four-belt era.

Only retired middleweights Bernard Hopkins and Jermain Taylor, former undisputed junior welterweight champ Terence Crawford, former undisputed cruiserweight champ Oleksandr Usyk and current undisputed junior welterweight champ Josh Taylor have earned that distinction thus far.

Alvarez (56-1-2, 38 KOs), of Guadalajara, Mexico, and Plant (21-0, 12 KOs), of Ashland City, Tennessee, will headline Showtime’s four-fight pay-per-view event from MGM Grand Garden Arena ($79.99). Caesars Sportsbook listed Alvarez as a 9-1 favorite Friday afternoon.

The official weights for the Alvarez-Plant pay-per-view undercard fights are listed below.

Showtime Pay-Per-View, 9 p.m. EDT; 6 p.m. PDT

Anthony Dirrell (32-2-2, 24 KOs), Flint, Michigan, 168½ pounds vs. Marcos Hernandez (15-4-2, 3 KOs), Fresno, California, 168½ pounds, 10 rounds, super middleweights.

Rey Vargas (34-0, 22 KOs), Otumba, Mexico, 125 pounds vs. Leonardo Baez (21-4, 12 KOs), Mexicali, Mexico, 126½ pounds, 10 rounds, featherweights.

Elvis Rodriguez (11-1-1, 10 KOs), Santo Domingo, Dominican Republic, 142 pounds vs. Juan Pablo Romero (14-0, 9 KOs), Villa del Carbon, Mexico, 143 pounds, 10 rounds, welterweights.

Keith Idec is a senior writer/columnist for krikya360.com. He can be reached on Twitter @Idecboxing.