The slugger from Longueuil, Que., put iron-chinned Don (Da Bomb) George down three times in the fifth and sixth rounds and then had to use some finesse before pulling out the victory in the 12th round of their IBF super-middleweight elimination bout on Friday night.
Referee Marlon Wright stopped the fight after Stevenson dropped George after 55 seconds of round 12, his fifth knockdown in the free-swinging bout that had the crowd of 4,251 on its feet to applaud both fighters when it was over.
"He is really tough," said 35-year-old Stevenson (19-1), a southpaw who managed to keep going despite injuring his left hand in the third round.
The match-up between two power punchers was expected to end early and looked like it would in the fifth when George (23-3-1) was dropped twice with heavy body punches. But he got up each time and ended the round with the two fighters trading blows in a wild brawl.
"It's not in my genetics to be a quitter," the Chicago-born George said. "I was disappointed the fight was stopped.
"I knew I was a far behind (on points), but if I was going to go out, I wanted to go out on my shield."
With the victory, Stevenson becomes mandatory challenger to IBF champion Carl Froch (29-2), the Englishman who took the title from Lucian Bute of Montreal in May. When that fight takes place is uncertain, as Froch has a tune-up bout with Yusef Mack on Nov. 17 and also is committed to a rematch with Bute.
George said this week that a loss may end his career, but his performance against Stevenson convinced his camp that he can still be a contender in the 168-pound division.
"What we learned is that has the heart and the ability to be a world champion," said George's promoter Leo Margules. "He got up three times from body shots.
"No one else in the world does that."
George said his ribs were badly injured and possibly fractured in the fifth, which left him unable to throw punches effectively with his right hand.
He went down again in the sixth and still got up, which raised alarm in Stevenson's corner that he may have spent his energy and would have none left for the late rounds.
But Stevenson spent the next five rounds staying mostly out of George's reach, circling his opponent and throwing right-hand jabs.
To start the 12th, Stevenson waved an arm in the air to get the crowd going and then went after George with both hands, stopping George before the limit for the first time in his career.
"Everyone thought I could only knock guys out in the first or second rounds, but I showed I can go 12 rounds," he said. "I wasn't tired at all."
Emanuel Steward, Stevenson's hall of fame trainer, missed the match, as the 68-year-old is recovering from surgery for a colon ailment. Javan (Sugar) Hill and Dereck Coleman took over his training.
"He's learned to box more with good balance and more power," said Hill. "He's learning how to control the fight more."
The bout was originally scheduled for Aug. 11, but was put off to Aug. 17 only to be postponed again when Stevenson suffered a hand injury in training.
In the co-feature, middleweight David Lemieux (27-2) of Montreal, still on the rebound from two losses in 2011, won a second straight fight convincingly, knocking down Alvaro Gaona (15-2) of Mexico late in the first round with a straight right and then knocking him out cold with a left hook only two minutes 48 seconds into the scheduled 10-round fight.
Promoter Yvon Michel said Lemieux would be featured on his next fight card Dec. 12 against a ranked opponent. The same card would have light heavyweight prospect Eleider Alvarez of Colombia against power-hitting veteran Edison Miranda.
Alvarez (10-0), the NABO light heavyweight champion, dropped Daniel Regi (15-7) with an uppercut and then put him down twice more in the second round to take the scheduled eight-round bout.
Light middleweight Kevin Bizier (18-0) of St-Emile, Que., returned from an 11-month layoff to drop Patrick Litkiewicz (6-1) of Poland in the first round with a left hook to the liver.
Irish light middleweight John O'Donnell (26-2) scored an eight-round decision over Thomas Mendez (16-3) of the Dominican Republic.
Heavyweight Didier Bence (6-0) of Montreal needed an eight-count when he was rocked in the first round but recovered for a six-round decision over journeyman Harold Sconiers (18-25-2).