Fatigue was the big factor in Saturday's fight between Sergey Kovalev and Saul "Canelo" Alvarez.
Canelo moved up in weight by two full divisions and scored an eleventh round knockout over Kovalev to capture the WBO light heavyweight title at the MGM Grand in Las Vegas.
After the fight, Kovalev admitted that he was tired after the conclusion of the sixth round.
At 36-years-old, Kovalev was unable to keep up a very active pace against the much younger man.
Sitting at ringside was a very interested observer at the MGM Grand, was Kovalev's countryman WBA light heavyweight champion Dmitry Bivol.
He felt Kovalev was no longer the same fighter of years back.
“If Kovalev would have met the same Alvarez four years ago - everything could have been different. Now it was clear that Sergey was fatigued. He boxed not that long ago, and he's not the same as he was years ago,” Bivol said to tass.
Bivol's co-promoter, Andrei Ryabinsky of World of Boxing, was proud of Kovalev's performance.
"Everyone saw the fight, Canelo boxed very well, Sergey lost, but I still think that Sergey is an excellent boxer and one of the best in the world,” Ryabinsky said.
“It was just that Canelo in this case was stronger and there were a lot of things [in his favor], right from the start of the fight. It's not a coincidence, they are both awesome boxers, but Canelo is now one of the best regardless of the weight category. And to lose to such an opponent is nothing to be ashamed of."
Luke Furman covers boxing for bokser.org.