Julio Cesar Chavez Jr. gets back into ring with a heavy challenge

The wait — and weight — is over for Julio Cesar Chavez Jr.

In September 2012, Chavez lost a one-sided but dramatic fight to Argentina’s Sergio Martinez, after which he was suspended for marijuana use. Saturday night, he climbs back into the ring after a year’s absence to fight Brian Vera at StubHub Center in Carson.

The non-title bout was originally contracted to be a super-middleweight fight with a weight limit of 168 pounds.

But Chavez (46-1-1, 32 knockouts) reported this week that he was at 173, and the fight’s promoters renegotiated for the new limit of 173 Friday after Chavez had said, “This is not a championship fight. I will be close to 168.”

Chavez, son of the legendary Mexican champion Julio Cesar Chavez, weighed in Friday at 172.4 pounds and Vera pumped on a few more pounds, too, weighing in at 171.2. As part of the negotiations, Vera’s camp had the fight reduced from 12 to 10 rounds.

Chavez promoter Bob Arum worked this week to deflect criticism from his boxer, who’s still trying to overcome the perception he’s coddled.

“He’s worked very hard, but I think with the layoff he was up way past 200 pounds,” Arum said. “He’s a big kid, and it’s been hard to come down.”

After recovering from a cut over his right eye that delayed this fight from happening on Sept. 7 at Staples Center, Chavez, 27, said he has embraced “this as the beginning of the second part of my career, and I’m very motivated to show everyone I want to be the best fighter in the world.”

Arum said if Chavez shows he can “step it up and prepare himself like a regular fighter,” he’ll look to 2014 dates against a veteran such as Arthur Abraham and a super-fight against 168-pound world champion Andre Ward.

“I want to see Julio aggressive, throwing punches to the body, being the crowd-pleasing fighter people love to see,” Arum said. “I want everyone to see he’s back.”

Those around Chavez say he’s more mature.

Chavez admits he made mistakes, smoking marijuana and caving in to the stress of things like weight cuts, aches and pains and the magnitude of the Martinez fight.

“I felt like I was working too hard and needed to relax,” Chavez said of his marijuana use. “I used something illegal, it was wrong and I got penalized.”

Martinez dominated their bout until Chavez rocked him and knocked him down in the 12th round. Martinez won by decision.

“I was very upset and angry with myself,” Chavez said of his layoff mood. “I didn’t come close to doing what I wanted to do in that fight. I guess if you go through a difficult time, you have to find a reason to learn from it.

“I want to regain the position where I was before the loss against Martinez. I am really looking forward to erasing all of those bad memories.”

Chavez has his father as an assistant trainer to new head trainer Vladimir Baldenebro.

“With my dad, he was always yelling and screaming from his seat in the crowd, so I said, ‘Let’s do it more professionally, come help me in the corner instead of making security tell you to get back in your seat,’” Chavez said.

Vera (23-6, 14 KOs) has twice defeated former super-welterweight champion Sergio Mora and said to “expect a war. We’re both prepared to come to fight and have great chins.”

The card also includes Russian middleweight Matt Korobov (20-0, 12 KOs) against Grady Brewer, with Arum hoping it leads Korobov to a fight against middleweight champion Gennady Golovkin.

Featherweight Oscar Valdez and light-welterweight Jose Ramirez, 2012 Olympians for Mexico and the U.S., respectively, will also fight in separate bouts.

lance.pugmire@latimes.com

Twitter: @latimespugmire