Jose Valenzuela viciously ensured Saturday night that there wouldn’t be any discrepancy about who won his rematch with Chris Colbert.

Valenzuela knocked Colbert unconscious with a sweeping right hook in the sixth round of their 12-round rematch on the David Morrell Jr.-Sena Agbeko undercard at The Armory in Minneapolis. His impressive victory enabled Valenzuela to avenge his controversial 10-round, unanimous-decision defeat to Colbert on March 25 at MGM Grand Garden Arena in Las Vegas.

The left-handed Valenzuela’s shot knocked Colbert cold, onto the bottom rope in the co-feature of the final “Showtime Championship Boxing” broadcast of the network’s 37-year tenure in the sport.

Referee Joel Scobie immediately waved an end to their second fight at 1:46 of the sixth round.

Valenzuela, who scored a knockdown during the first round again Saturday night, improved to 13-2 and recorded his ninth knockout. Colbert (17-2-1, 6 KOs) suffered the first knockout defeat of his eight-year pro career.

Brooklyn’s Colbert, 27, got up from a knockdown less than 30 seconds into their first fight and made it very competitive March 25 in Las Vegas. He landed a lot of jabs, withstood Valenzuela’s power until the final bell and won by the same slim margin, 95-94, on the scorecards of judges Glenn Feldman, Lisa Giampa and Don Trella.

Valenzuela vehemently protested the official result during his post-fight interview in the ring. Colbert embraced the rematch because he wanted to prove his superiority over Valenzuela by winning their second fight more convincingly.

The 24-year-old Valenzuela, of Renton, Washington, told BoxingScene.com recently that he underwent surgery after an accident he wouldn’t detail two weeks before he fought Colbert 8½ months ago. Valenzuela believes that injury significantly impacted his conditioning, which seemed better Saturday night.

Valenzuela’s left uppercut landed a little less than 20 seconds into the sixth round. The abrupt end came a little more than a minute later.

A right uppercut by Valenzuela caught Colbert and he followed up with a right hook just after the midway mark of the fifth round.

Colbert and Valenzuela slipped plenty of punches during the fourth round, but Colbert’s jab was effective during those three minutes.

A left-right combination by Valenzuela landed when Colbert was backed into the ropes just before the third round ended. An overhand left by Valenzuela knocked Colbert backward with just under 1:20 to go in the third round.

Valenzuela landed a straight left a little less than 30 seconds into the third round. Fighting from a southpaw stance, Colbert caught Valenzuela with a right hook several seconds later.

Much like their first fight, Colbert got back into their rematch during the second round after getting dropped during the first round.

Valenzuela blitzed Colbert again and landed a left uppercut that hurt him barely 30 seconds into the opening round. Valenzuela also landed a flush right hook in that sequence.

Colbert went into a squatting position. Scobie believed the ropes held Colbert up and therefore called a knockdown with just under 2:20 to go in the first round.

Colbert tried to hold and move his way out of that serious trouble, but Valenzuela kept coming forward. Colbert caught Valenzuela with a right-left combination that temporarily stopped Valenzuela from punching with about 1:15 to go in the first round.

Colbert got his legs under him by the time the first round ended and made it to the second round.

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