TORONTO — Georges St-Pierre feels (Rowdy) Ronda Rousey’s pain like perhaps no other.

Eight years before Rousey was dethroned by Holly Holm at UFC 193, St-Pierre lost his welterweight crown to Matt (The Terror) Serra at UFC 69 in a shocking upset of his own.

Serra was an inflated lightweight, albeit one with a big right hand and a black belt in Brazilian jiu-jitsu. A happy-go-lucky sort, Serra (8-4) had to win a season of "The Ultimate Fighter" reality TV show devoted to veterans making a comeback just to earn a title shot.

St-Pierre, then 13-1 as a pro, was a 10-1 favourite to dispatch Serra. The Montreal MMA star was seen as younger, bigger and faster, with more weapons at his disposal. And he had just avenged a 2004 loss to Matt Hughes, widely viewed as the greatest welterweight champion ever, to claim the 170-pound crown at UFC 65 in November 2006.

Serra needed just three minutes 25 seconds in April 2007 to dethrone St-Pierre in his first title defence.

"This is my worst nightmare," St-Pierre said that night in Houston.

The previously unbeaten Rousey, who went into last weekend’s fight as MMA’s reigning rock star, is living her own nightmare now — a 20-1 favourite left unconscious and bleeding.

"It’s unfortunate for Ronda but I’m happy for Holly in the same time," St-Pierre, who like Holm had coach Greg Jackson in his corner, said in an interview Thursday.

"In this game, no one’s invincible," he added. "Sometimes you zig when you should zag."

St-Pierre lost his confidence along with his championship belt, but eventually remade both his game and the people around him.

"I needed to beat a lot of my own demons, a lot of my fear," he said. "And I came back stronger.

"So in a way for Ronda it’s sad that she lost, but maybe it could be the best thing that ever happened to her, in that she will come back much stronger."

St-Pierre did. He won 12 fights in a row after losing his title, thumping Serra at UFC 83 in April 2008 to regain his crown. He stepped away from the sport in late 2013 and, now 34, says he has yet to decide whether he will come back.

While both St-Pierre and Rousey fell victim to huge upsets, their cases are different.

The Canadian was a newly crowned champion. Rousey had made five successful title defences and had been demolishing all comers.

Holm was a different story, however — a former world-class boxer with some of MMA’s best coaches behind her.

While Rousey looked in trouble from the get-go against Holm’s movement and slick striking, St-Pierre had been doing well against Serra until the unthinkable happened.

After Serra caught him a right to the back of his head, St-Pierre lost his equilibrium and fell backwards.

Former champion Hughes was ringside at the Toyota Center to witness the massive upset.

"He’s hurt," Hughes, writing in his book "Made in America," recalled thinking. "Wait a minute. He can’t be hurt. He’s fighting Matt Serra."

The end quickly followed.

The defeat rocked St-Pierre, who said he used to feel no fear preparing for fights.

"The fact that I lost made me realize that I was a human being," he said. "It was very hard to come back from a loss. I needed (the help of) a sports psychologist. Because what is very important to a fighter is the confidence and sometimes with a loss like this, you can lose your confidence."

On the advice of sports psychologist Brian Cain, St-Pierre looked to rid himself of the mental albatross of his title defeat by scrawling Serra’s name onto a brick and hurling it into the icy waters off the South Shore.

"Actually I thought it was kind of weird but I felt better after," St-Pierre said.

St-Pierre’s preparations for the Serra fight had been wretched. His father was seriously ill and a cousin was in a coma after a car accident. There were other family issues.

Injuries cut into his preparation. And as champion, his attention wandered.

"Let’s just say he partied a little bit too much," former manager Stephane Patry said at the time.

"It taught me what it takes to become world champion," St-Pierre said after the loss. "And when I lost to Matt Serra, it taught me what it takes to stay world champion.

"You know when you become world champion at 25 years old and everybody around you — in the gym, everywhere — tell you how great you are and things like that, it makes you believe that you’re in a box that separates you from the other fighters. But this box, this line is an illusion. And that’s what happened. Even though I’m not a cocky guy, I got caught in those situations, many other things. I made many mistakes."