Russia's Denis Lebedev, right, hammers Roy Jones Jr. just before the bout is stopped in the 10th round. ((Sergey Ponomarev/Associated Press))

Cruiserweight contender Denis Lebedev scored a frightening knockout on Saturday over Roy Jones Jr., once the top boxer in the world.

With seconds remaining in the 10th round of their bout in Moscow, Jones retreated to the ropes, where Lebedev landed a series of big punches before referee Steve Smoger stopped the fight belatedly.

Jones (54-8) lurched forward and was actually suspended in midair before falling face first. The Pensacola, Fla., native lay on the canvas for nearly two minutes before being able to get to his feet.

Once the best pound-for-pound fighter in the world for a period of years beginning in the mid-1990s, the 42-year-old Jones has won just five of his last 13 fights. He lost his light heavyweight title on a one-punch knockout in May 2004, lost consciousness in a defeat four months later against Glen Johnson, and was steamrolled in one round in late 2009 against Aussie Danny Green.

Despite the manner in which he was defeated, Jones  wouldn't guarantee retirement.

"I really don't know what I'm going to do now," Jones said. "I'm going to think about it."

The Russian Lebedev (22-1) is looking to get another title shot after losing a narrow decision to Germany's Marco Huck.

 "I'm so happy with this win, we put so much into this fight," Lebedev said. "Jones was everything we expected: quick, strong, cheeky. … But I pulled through."

With files from The Associated Press