LAS VEGAS – Marc Castro continued the developmental phase of his career in impressive fashion on another Canelo Alvarez undercard Saturday night.

The lightweight prospect from Fresno, California completely controlled the action against Kevin Montiel Mendoza before Castro viciously knocked out Montiel with a right uppercut in the fifth round on the Alvarez-Gennadiy Golovkin undercard at T-Mobile. Referee Tony Weeks immediately waved an end to their scheduled eight-rounder at 1:40 of the fifth round, as soon as Mendoza fell flat on his back.

The 23-year-old Castro improved to 8-0 and recorded his sixth knockout. Mexico’s Mendoza (6-2-2, 3 KOs) lost by knockout for the first time in 10 professional fights.

In the round prior to Castro’s knockout, Weeks warned Castro for a clubbing right hand he landed to the back of Mendoza’s head 30 seconds into the fourth round. Castro connected with several right hands during the remainder of a one-sided fourth round.

A right hand by Castro landed with 25 seconds to go in the third round.

Castro cracked Mendoza with a thudding right to his body 1:15 into the second round. Castro caught Mendoza with a stiff jab and then a left hook up top just before the second round ended as well.

Castro was busy and accurate throughout a first round he dominated. Mendoza came forward for most of the opening round, but he didn’t land many clean punches during the first three minutes of their fight.

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