LAS VEGAS – Justin Viloria’s power and speed were too much for Pedro Pinillo to handle Saturday.

The 18-year-old southpaw from Whittier, California battered Pinillo for three-plus rounds, until referee Thomas Taylor determined Pinillo had taken too much punishment. Taylor stopped their six-round junior lightweight fight at 1:41 of the fourth round on the Rolando Romero-Ismael Barroso undercard at The Cosmopolitan of Las Vegas.

Viloria, a nephew of former flyweight and junior flyweight champ Brian Viloria, improved to 2-0 and recorded his second knockout as a pro. Colombia’s Pinillo (5-2, 5 KOs) lost inside the distance for the first time in seven professional fights.

Viloria and Pinillo traded at the start of the fourth round. Pinillo, bleeding from his nose, tried to hold Viloria with about 1:40 to go in the fourth round.

Viloria broke free from his grasp and unloaded an array of power punches that made Taylor step between them to halt the bout.

Viloria landed three right hooks in a row with just under 1:15 on the clock in the third round. Pinillo landed flush punches of his own in the third round, but nothing that prevented Viloria from coming forward.

A right hook by Viloria made Pinillo take a step backward with just under 30 seconds remaining in the second round. Viloria’s hard left to Pinillo’s body made him cover up several seconds after the midway mark of the second round.

A left hand by Viloria knocked Pinillo off balance with just over 1:20 to go in the opening round. Pinillo seemed affected by several other punches Viloria landed during the opening round.

In the first fight on the card Saturday, 18-year-old welterweight prospect David Whitmire unanimously out-pointed Javier Vargas in their four-rounder.

Whitmire (2-0, 1 KO), of Washington, D.C., won by the same score, 39-37, on all three scorecards. Vargas, of McAllen, Texas, slipped to 3-2 (3 KOs).

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