Julio Cesar Chavez Jr. looks to cement his legacy in bout with Canelo Alvarez

There might be a resemblance to the same aloof Julio Cesar Chavez Jr., but those close to the fighter say lessons found in growing up have transformed him.

This week, Chavez Jr. has worn over-sized sunglasses and a Rastafarian stocking cap to sessions with reporters. So forget about any idea that he’s hellbent to distance himself from the past couple marijuana positive samples he produced.

Yet, the accounts from his former-champion father, his legendary Mexican trainer Nacho Beristain and Chavez’s longtime assistant manager paint the fighter as a new man whose reinvention could arrive in a stunning Saturday night victory.

“He has one-thousand percent turned a corner, and why? Canelo Alvarez,” said Chavez Jr.’s assistant manager, Sean Gibbons. “He’s told me, ‘I grew not to like boxing. I kept doing it because I was Chavez Jr. and because they were paying me big bucks. …’

“He needed something to bring him back and he’s found it in pride, legacy and country.

“He knows he can’t lose to Canelo. Because if he wins, he’s no longer going to be Junior. He’s going to be himself.”

The overwhelming burden of taking on a fighting career after his father’s iconic dominance has always seemed like an impossible undertaking.

One day in training, Julio Cesar Chavez Sr. stormed in on his son’s session and began heatedly scolding him over fundamentals, prompting the son to exclaim, “If you weren’t there to raise me, don’t come now and tell me what to do!”

Even though he rose to become a middleweight world champion in 2011, Chavez Jr. soon after succumbed to the strain in well-publicized missteps of lax training, weight problems and dirty tests.

But sometime after a knockout loss to Andrzej Fonfara in Carson in 2015, Chavez Jr. turned 30 and looked into the eyes of his new-born daughter, Julia, now 3, and found needed peace and inspiration.

Friends say he paused to reflect on the profound requirements of parenthood and discovered a new appreciation in how to view his own national-hero father, who struggled with drug addiction as his fight career closed, but has been clean for seven years now.

Chavez Jr., 31, won his past two fights and intensified his pursuit by signing to meet rival countryman and former two-division champion Alvarez (48-1-1, 34 knockouts) and by aligning with Beristain, who trained him in the mountains high above Mexico City.

“He noticed he was on the wrong path. He noticed this was the right moment, so he can follow that path his father had started — the path he loved from the beginning,” Beristain said.

The standard of being Chavez Jr. “affected him in one way or another, but I believe it’s been corrected,” as Chavez Sr. has eased off his demanding ways.

“He wants to prove he has the pride that Mexico expects,” Beristain said.

Chavez Jr. (50-2-1, 32 KOs) insists he will not fight Saturday as he did in losing his middleweight belt to former champion Sergio Martinez in 2012, when his downward slope began with 11 lethargic rounds before he nearly knocked out Martinez in the 12th.

“I go over my mistakes,” Chavez Jr. said. “I’m more determined. I trained harder. I’m more prepared. … This is an important fight, an important moment, an opportunity at the right time. This can be the big boost in my career if I win.

“I have more fight and life experience. I’m in a better place. This is an opportunity to show the people.”

In camp, Chavez Sr. showed up to watch, holding his tongue.

“I asked him to be in shape, the best shape he can be in,” for Alvarez, Chavez Sr. said. “Because I know about his capacity. He can do that. Nacho really pushed Julio. I saw him running, getting into shape, and I just loved that.

“I see a tough fight, but if Julio gets in the ring with a lot of heart and a lot of [guts], he’ll do it.”

Gibbons said Chavez Jr. has maintained a joyful demeanor from the day he agreed to fight Alvarez, well aware that victory in maturity washes away so many of those imperfect, youthful steps.

“There’s a lot of pressure on both of us,” Chavez Jr. said. “I come prepared.”

lance.pugmire@latimes.com

Twitter: @latimespugmire