Sergey Kovalev goes the distance against Eleider "Storm" Alvarez to win the rematch and regain his light heavyweight world title belt. (0:40)

FRISCO, Texas -- Six months after Sergey Kovalev lost his light heavyweight world title by upset knockout to Eleider "Storm" Alvarez, he regained it in clear unanimous-decision fashion in the main event of the Top Rank Boxing on ESPN+ card Saturday night.

Kovalev, who called the first loss "an accident" and said he ran out of energy as they went into the second half of the fight because he had overtrained, suffered no such issues this time around before 4,877 at the Ford Center at the Star, the training facility of the Dallas Cowboys.

Many thought Alvarez would repeat his victory, but Kovalev won by scores of 116-112, 116-112 and a surprising shutout score of 120-108. ESPN also scored the fight 116-112 for Kovalev, who is now a three-time light heavyweight titleholder.

"I'm thrilled. It's sweeter when nobody thinks you can do it," said Main Events CEO Kathy Duva, Kovalev's promoter.

Last Aug. 4, Alvarez was trailing on all three scorecards when he rallied to score three knockdowns in the seventh round for an upset knockout victory to take Kovalev's 175-pound world title in Atlantic City, New Jersey.

Kovalev quickly exercised his option for an immediate rematch and stuck by his view that he had overtrained and would turn the tables in the sequel.

He ended his three-fight stint with trainer Abror Tursunpulatov and hired veteran trainer Buddy McGirt, the former two-division world titleholder and newly elected International Boxing Hall of Famer, along with strength coach Teddy Cruz. The two of them were brought in to help revive the career of the late Arturo Gatti and were hired to do the same with Kovalev.

But besides the changes in his camp, Kovalev came into the fight facing serious issues outside the ring. He faces a maximum of four years in prison because of a felony assault charge stemming from a June 9 arrest because of an incident in Big Bear Lake, California, in which he is accused of punching a woman in the face after she rejected his sexual advances. He is due back in court next month for a preliminary hearing and has declined to discuss the incident.

"Who's ready for a unification fight? I'm here to make history for me and my fans," Sergey Kovalev said after his win over Eleider Alvarez. Mikey Williams/Top Rank

But if it was on his mind, it sure did not appear that way in the fight, and when it was over McGirt was elated.

"I'm very happy," McGirt said. "He adjusted well. He stuck to the game plan more than I anticipated he would, but I kept reminding him to keep it basic, keep it basic. I thought it was close, but I felt he won."

Kovalev gave the credit to his new training team.

"This training camp I had help from my team, Buddy and Teddy. Thank you guys for this," Kovalev said. "They stopped me from overtraining. I saved my energy and I'm happy. We worked on the jab. Always my jab and right hand."

Duva, who promoted Gatti throughout his career, said she wanted Kovalev to go to McGirt and Cruz following his decision loss to Andre Ward in their November 2016 first fight.

"Sergey has known since the first Ward fight that he was doing something wrong [in training]," Duva said. "It took him until this camp to do what I wanted him to do, which was to bring in Buddy and Teddy. Sergey ate [on Friday] before the weigh-in. He didn't dehydrate one ounce. He was in great shape."

The fight began at a measured pace but each man landed a couple of good shots, including Alvarez landing the best punch of the round, a left hook to the head in the final seconds. Kovalev responded with a strong second round as he landed right hands and jabs to force Alvarez back.

Final punch stats Fighter Total Jabs Power Kovalev 213 of 816 (26%) 60 of 391 (15%) 153 of 425 (36%) Alvarez 111 of 369 (30%) 33 of 203 (16%) 78 of 166 (47%) -- Courtesy of CompuBox

Kovalev appeared in control by the fifth round as he landed stiff right hands and jabs while Alvarez threw sporadically. It had the feel of the first fight when Kovalev opened the big lead before being stopped.

They began to trade more in the sixth round, but Alvarez seemed to get the better of the action thanks to his right hand. Alvarez (24-1, 12 KOs), 34, a Colombia native who has spent his entire pro career fighting out of Montreal, landed a good right hand late in the seventh round. Kovalev took it well, unlike in the first fight.

Kovalev (33-3-1, 28 KOs), 35, a Russia native fighting out of Los Angeles, had a big burst of offense late in the ninth round. He landed several punches and by the end of the round Alvarez's nose trickled blood.

The 10th round was one of Kovalev's best of the fight. Inside the final minute of the round, he rocked Alvarez with a left-right combination and Alvarez did very little thereafter. After the 10th round, Alvarez was told in his corner that he needed a knockout to win the fight.

Unlike the first fight energy issues, Kovalev still had a bounce in his step in the final round and looked energetic while it was Alvarez who appeared tired as he took punches, including a thudding right hand to the head at the final bell.

"I have no excuses," Alvarez said through an interpreter. "I know if it went the distance he would be the favorite so I tried to press the fight. I thought I put on a good performance, but I just did not get the result. I don't see myself as a loser, but I do give him credit. He went out and proved he wanted to win the fight."

Kovalev landed 213 of 816 punches (26 percent) and Alvarez connected with 111 of 369 shots (30 percent), according to CompuBox statistics.

With the win in hand and a belt back around his waist, Kovalev, still the biggest name in the division, will have plenty of options as long as his legal issues don't derail him. Top Rank, which has options on future fights in its partnership with Main Events, promotes world champion Oleksandr Gvozdyk, world titlist Artur Beterbiev and super middleweight titlist Gilberto "Zurdo" Ramirez, who is moving up to light heavyweight for his next fight.

"There are so many choices. We will sit down with our friends at Top Rank and talk about it, but I don't think were going to have any trouble finding an opponent," Duva said.

Kovalev said he would not be picky.

"For me it doesn't matter. Who's ready for a unification fight? I'm here to make history for me and my fans," Kovalev said. "I want to fight the champions in my division. Any fighter who is ready."