Stevenson took exception to Bellew calling him "a pimp." On Thursday, the six-foot-three British boxer had called the five-foot-10 Stevenson "a dwarf."
The tension came to a head after the weigh-in — both clocked in at 175 pounds — when they did the traditional face-to-face. Bellew apparently gave Stevenson a tap on the head as some of his fans chanted "pimp, pimp, pimp."
It was an apparent reference to the 18 months the Haitian-born slugger from Montreal once spent in a Quebec jail on charges of managing prostitutes, assault and uttering threats.
The two boxers scuffled and had to be pulled apart.
''He put his head on my head, he shoved his head in my nose, so I smashed my head right back in his nose and I told him what I think of him," Bellew said afterward. "That's all that happened."
Stevenson had another version of events. He said Bellew acted out of fear and disarray.
"The guy is desperate," Stevenson said.
"When I got to the face-to-face, he gave me a hit and I wanted to give him one back. I wanted to rip his head off but my team held me back. I know he's scared, he tries to hide his fear. I saw fear in his eyes."
Bellew (20-1-1, 12 knockouts) is competing in his first professional bout outside the United Kingdom. He is a former Commonwealth champion who lost a previous world title attempt by majority decision to WBO champ Nathan Cleverly in Liverpool in 2011. He has won five fights in a row since then.
He doesn't mince his words when it comes to his opponent, the only Canadian with a world title from one of the major sanctioning bodies and one of the rising stars of boxing with his devastating punching power.
''I think he's a little scrote," Bellew said. "He's a maggot. I don't like what he's about....The minute I called him a pimp, he exploded.
''If you call me a Scouser, I'm a Scouser, I'm from Liverpool. That's what a Scouser is. If I call him a pimp, he's a pimp. That's what he's done. There's no ifs or buts. That's what he's done. That's a fact. That's not me saying he's this, he's not a nice guy. That's speculation. I called him what he is. That's what he was.''
Stevenson (22-1, 19 knockouts) won the WBC belt and The Ring magazine title as linear champion with a thundering left hook only 76 seconds into his bout with American Chad Dawson in June.
The southpaw followed that on Sept. 28 by pounding former IBF champ Tavoris Cloud so badly that the challenger quit after seven rounds. Bellew was in the Bell Centre audience for that one.
Bellew became mandatory challenger with a 12-round decision over Isaac Chilemba in May.
While Stevenson may call himself Superman, Bellew doesn't see him as a Man of Steel.
''I have a better boxing brain than him," he said. "This guy's got 20 guys around him telling him he's great, he's Superman. He ain't Superman. He's a human being with two arms and two legs. Add to that he's a midget compared to me. He can't beat me.''
The bout will be held Saturday at the Colisee Pepsi.
The co-feature will be another light heavyweight title clash between hard-hitting Russian Sergey Kovalev (22-0-1), the World Boxing Organization champion, and Ismayl Sillakh (21-1) of Ukraine. The bouts are to be aired on the U.S. specialty channel HBO.