LAS VEGAS — Sergey Kovalev was in control.

He knocked Andre Ward down in the second round, and was dictating the action with his measured jab.

Then Round 5 hit and Kovalev felt … different.

Kovalev said he was exhausted, that he felt like he left everything in training camp. The 34-year-old Russian says a month before the fight, he knew: his gas tank was empty.

Under the direction of a strength and conditioning coach that both Kovalev and Main Events CEO Kathy Duva couldn’t recall the name of, Kovalev overtrained and he says it resulted in a flat second half of the bout, which he lost via controversial decision.

“He fought an empty Kovalev,” the former light heavyweight champ said of Ward. “I fought first time on this level, HBO Pay-Per-View, and I had a lot of pressure. I wanted to get in best shape for my fight and one month before the fight I had no energy. I overtrained — I pushed, pushed and pushed. I believed my coach would stop me on time from overtraining.”

Duva says Kovalev would often run 14 miles a day. That Kovalev would conduct a three-hour training session, then train two more times later that day. He was on weight one month before the fight, and his face was grey, according to Duva.

Kovalev said he had  his own concerns a month out, but that telling manager Egis Klimas and Duva that he wanted to withdraw and say “I’m not ready” for the biggest fight of his career wasn’t an option.

“You want to punch, but you can’t punch because you have no energy,” he said. “My tires went flat; speed lost. I sat down in the corner and I wasn’t happy. Why did I have this guy in my camp? (Ward) is nothing, he’s easy to fight.

“When your car has no gas and is empty, it won’t ride,” Kovalev explained. “It was the same for me. I don’t know how my body had energy for another six rounds.”

This camp, Kovalev stated, was a different matter. He hired Aleksandr Mikhailovich, who trains biathletes, to oversee strength and conditioning in preparation for the rematch. Kovalev’s resting heart rate for the Ward fight was 65. It’s 40 for this camp. Now, Kovalev says, he feels “full” ahead of his fight Saturday on HBO PPV.