Willie Jones viciously knocked out an undefeated opponent in the first round Saturday night.

A perfectly executed counter left hook by Jones knocked Derrick Jackson unconscious in a junior middleweight fight that was scheduled for eight rounds at The Armory in Minneapolis. Referee Mark Nelson immediately waved an end to the action as soon as Jackson went down with 1:39 to go in the first round.

Jones, of Burlington, North Carolina, upped his record to 9-2 and recorded his sixth knockout. Jackson, of Orlando, Florida, lost for the first time in 11 professional fights (10-1, 5 KOs).

Showtime streamed Jones’ spectacular knockout as part of the Subriel Matias-Jeremias Ponce undercard on its YouTube channel.

Jackson remained flat on his back for several minutes, but he was eventually helped to his feet.

Earlier Saturday night, Mickel Spencer was too active, too accurate and too strong for Margarito Hernandez in Spencer’s third professional fight.

The 18-year-old Spencer dropped Hernandez with a right hand and beat him by technical knockout late in the first round of their junior welterweight fight. Spencer, of Linden, Michigan, improved to 3-0 and produced his second knockout.

Hernandez, of Wapato, Washington, fell to 3-5-1.

Spencer hammered Hernandez with body shots after the midway mark of the opening round. He later drilled Hernandez with an overhand right to his chin that sent Hernandez flat on his back with 44 seconds to go in the opening round.

Schorle stopped their scheduled four-rounder as soon as Hernandez went down.

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