Former four division world champion Roy Jones Jr. believes Sergey Kovalev "is done" after watching the feared Russian puncher get knocked out in the seventh round by undefeated Eleider Alvarez, on Saturday night at the Hard Rock & Hotel in Atlantic City.

After losing back to back fights to Andre Ward, Kovalev rebuilt his career in the last 10 months by regaining the WBO light heavyweight world title, and securing knockout wins over Vyacheslav Shabranskyy and Igor Mikhalkin - who were both a level or two below Kovalev.

Alvarez, who was boxing very well in the fight, dropped Kovalev three times in the seventh round before the contest was waved off. 

The 35-year-old 'Krusher' lost his WBO title and slumped to a 32-3-1 record, with Alvarez rising to 24-0.

Alvarez initially floored Kovalev with a big right hand in the seventh.

And although the Russian fighter managed to get to his feet and beat the count, a brutal left hook and then a right returned him to the mat and confirmed his demise.

Kovalev got up a second time and the fight was allowed to continue, but Alvarez quickly sent him down a third time - which prompted the referee to quickly wave it off.

Jones was watching the fight from ringside as part of the HBO broadcast team.

He had a sense in the early rounds that Kovalev was not very comfortable with Alvarez's fighting style.

"Like I said early in the fight, I didn't like how Kovalev was looking [with his facial and physical reactions]. Those jabs [from Alvarez], when that were throwing off [Kovalev's] timing and putting him off-balance with the jabs. Those types of things let me know something about a fighter. When I see that, I don't like it," Jones said.

"Alvarez has been waiting in the wings for over five years now. He knew it was his time. And what we wanted to see is if the fire fizzled out [from Alvarez waiting too long] or did he still have the fire. If he still had the fire, could he withstand the early onslaught [from Kovalev]. We knew that if he could weather the storm, he could get Kovalev."

When asked if he felt Kovalev was done after this stunning loss, Jones replied - "Yes, I think Sergey Kovalev is pretty much done at 35."