TORONTO - Lyoto (The Dragon) Machida used to be the champion enigma in the UFC. At least until Mauricio (Shogun) Rua solved the Machida puzzle.

Now Machida (17-2) finds himself up against Jon (Bones) Jones, the current light-heavyweight champion. Now it is Jones whose unique fighting style is leaving opponents battered and broken.

The present and former title-holders will face off in the main event of UFC 140 on Dec. 10 in Toronto, UFC president Dana White announced Thursday via Twitter.

The news comes one day after White shot down reports that Rashad Evans would face Jones at the Air Canada Centre. Evans, a former 205-pound champion himself, is next in line to face Jones but has again been sidelined again by injury.

When Machida defeated Evans for the title at UFC 98 in May 2009, commentator Joe Rogan famously noted the start of the "Machida era."

Once criticized for playing it safe, the Brazilian was clinical in putting away Evans in the second round.

He hurt Evans with a left and pounced, firing more than 30 strikes in some 30 seconds at the dazed champion. Machida eventually connected flush with a left to the chin and Evans toppled at the fence as if his legs had suddenly been removed.

Opponents were pondering how do you hit him, rather than how do you beat him.

"There's no puzzle like Machida," middleweight Chael Sonnen said after the Brazilian won the 205-pound title.

But Rua ended the Machida reign two fights later -- losing a disputed decision before knocking the champion out in the rematch -- using his powerful kicks and punches to connect and damage his fellow Brazilian.

One fight later, Jones dismantled Rua to take the title at UFC 128.

Now Jones is the MMA riddle no one has solved.

At six foot four and with a huge wingspan, he is near impossible to get close to if he doesn't want you to.

He is also unpredictable, lashing opponents with kicks, punches or elbow strikes from all angles. And he can wrestle, thanks to his junior college championship days.

"He's going out there and he's keeping people guessing from Round 1 to Round 5," bantamweight champion Dominick Cruz said recently. "He never comes out the same way, he never throws the same combination, it's always switching it up. And he's always threatening."

Throw in a top trainer in Greg Jackson and you have one tough package.

While Jones (14-1) has a loss on his record, it came by disqualification (for an illegal elbow) in December 2009. Matt Hamill got the win but needed surgery after the bout, which saw him tossed around the cage like a ragdoll.

Nicknamed the hammer, Hamill was the nail against Jones.

Machida's style is based on his family's brand of karate, which is all about defence. It harkens back to olden days when warriors fought with swords. One hit could cause death.

Machida has travelled the world to add to his arsenal -- wrestling in Japan, Muay Thai in Thailand, even sumo.

After beating Evans for the title, Machida was considered at the top of his game. He was 15-0 as a pro fighter (7-0 in the UFC) and had never been knocked down. He had yet to lose a round in the Octagon.

Machida, who at six foot one is modestly sized for a light-heavyweight, had also absorbed fewer strikes than any other fighter in UFC history at the time (among those with at least five bouts).

When it came to attack, Machida was second only to middleweight champion Anderson Silva in striking accuracy. Machida had a 65 per cent hit rate, compared to the fighter average of 35 per cent.

And only welterweight champion Georges St. Pierre was better at resisting takedown attempts than Machida (84 per cent).

Machida has used a peekaboo style to great effect in the past, darting in to attack and then moving out of range. Until Rua.

Machida has gone 1-1 since losing his title, dropping a razor-thin decision to Quinton (Rampage) Jackson at UFC 123 and knocking out Randy Couture with a savage front kick to the face at UFC 129 in Toronto in April.

The Couture win has restored some of his aura, albeit that it came against an aging legend.

Evans' title wait continues, meanwhile.

He issued a statement Thursday saying he is recovering from a dislocated thumb suffered after his last fight, a win over Tito Ortiz. Pins inserted into the thumb were only removed Wednesday and Evans said he was told he needed another three weeks before being able to use his hand in training.

"I fully understand his (White's) decision to put Machida against Jones for the title at UFC 140," Evans added. "Given the rehabilitation time I require for my dislocated thumb, I would not be 100 per cent ready by Dec. 10."

Machida agreeing to step up is a reversal of earlier this year, when he apparently backed out of an agreement to fight at UFC 133, replacing the injured Phil (Mr. Wonderful) Davis.

An irritated White said Machida agreed to fight and then his camp came back and asked for "Anderson Silva money."

Machida later said he asked for more money because he was being asked to take the fight on short notice and to move his training camp to the U.S. from Brazil.

Ironically the UFC 133 offer was to fight Evans. Tito Ortiz accepted the fight when Machida backed out, losing by second-round TKO.