By Keith Idec

LAS VEGAS – David Lemieux needed less than one round to silence Spike O’Sullivan on Saturday night.

Lemieux’s crushing left hook knocked out O’Sullivan late in the first round of their scheduled 12-round WBA middleweight championship elimination match on the Canelo Alvarez-Gennady Golovkin undercard at T-Mobile Arena. Ireland’s O’Sullivan went down to his gloves and knees after absorbing that brutal blow.

Referee Russell Mora took one look at the stunned O’Sullivan as he attempted to get up and stopped the fight at 2:44 of the first round. Montreal’s Lemieux became the WBA’s mandatory challenger for the winner of the Alvarez-Golovkin rematch later Saturday night.

The 29-year-old Lemieux improved to 40-4 and recorded his 34th knockout while elevating himself back into position to fight for a middleweight title.

The former IBF middleweight champion also proved his superiority over Ireland’s O’Sullivan, who talked a lot of trash before their fight. O’Sullivan called Lemieux “a greasy piece of sh*t” during a press conference Thursday at MGM Grand.

“Don’t piss me off, guys,” Lemieux told HBO’s Max Kellerman in the ring following his impressive victory. “I guess the message should be clear. I didn’t like all that trash-talking that was done to me before the fight by O’Sullivan. … I don’t trash talk at all. I don’t respect that type of behavior.”

The 34-year-old O’Sullivan (28-3, 20 KOs) was knocked out cleanly for the first time in his 10-year pro career. England’s Chris Eubank Jr. stopped him after the seventh round in their December 2015 bout, in which O’Sullivan didn’t come out of his corner for the start of the eighth round.

His first defeat came against WBO middleweight champ Billy Joe Saunders, who out-boxed him in their 12-round fight in July 2013. England’s Saunders (26-0, 12 KOs) also expertly out-boxed Lemieux on December 16 in Laval, Quebec, Canada.

Keith Idec is a senior writer/columnist for krikya360.com. He can be reached on Twitter @Idecboxing.