Canelo Alvarez is deep in the final weeks of work before he meets Gennady Golovkin on Sept. 15 in a middleweight title rematch. It’s the most compelling fight of the year and the possible culmination of a sports rivalry that has turned into a bitter personal grudge.

Alvarez’s suspension for failing two drug tests earlier this year is the primary source of this animus. It’s the reason the fight was postponed four months, costing both fighters untold millions, and it’s the reason the Mexican champion has been out of the ring for the longest stretch in his 13-year professional boxing career.

“This is my biggest fight, and this is starting a new chapter, a second chapter in my career,” Alvarez said. “It’s going to be a big victory for me, and I’m going to come out of it with a new energy.”

Alvarez goes through a workout both crisp and familiar, with trainer Eddy Reynoso monitoring each move.

Chepo Reynoso, Eddy’s father and the veteran boxing trainer who now manages Alvarez’s career, smiles at the familial vibe, along with the loving interplay between the fighter and his daughter.

“When so many (bad) things happen, you become immune,” Reynoso said. “Venom doesn’t kill you. It fortifies you.”

After making what he insists was an inadvertent mistake by eating tainted meat in Mexico, Alvarez is determined to reassert his supremacy, and to reclaim his reputation. He acknowledges the correctness of his punishment, but he’s also eager to reach a point when he isn’t talking about it every day.

“The negativity doesn’t get through to me,” Alvarez said. “I always focus on what I’m doing. I have to think about the fight. If (Golovkin) is thinking about me all the time, he’s not thinking about the fight.”

“Actions speak louder than words. Yeah, it bothers me, but I’m going to use it to energize me and motivate me and inspire me to go harder. They’re going to understand all the fuel they gave me.”

The rematch, set for May 5, was a natural for both — but then Alvarez tested positive for clenbuterol in February.

Alvarez withdrew from the bout, which was only rescheduled after months of negotiations and a reconfiguring of the financial terms. All the while, Golovkin and his trainer, Abel Sanchez, lobbed increasingly vicious verbal assaults at Canelo’s camp, believing Alvarez had knowingly cheated.

When asked at the public workout if he would shake Golovkin’s hand in sportsmanship after their bout, Alvarez said: “For me, it’s very difficult, especially after all the things that have been said, all the offensive claims. That’s going to be very hard for me. I don’t know.”

Eddy Reynoso wants his fighter to throw more punches in the rematch while still avoiding a slugfest that could make both fighters vulnerable to a knockout.

“We’re going to keep the defense, but be more active,” Reynoso said. “He’s going to throw better combinations, and he’s going to think about counterpunching much better. We’ve been working on it every day. When Golovkin throws punches and misses, that’s when Canelo needs to stop him.”