LAS VEGAS – Diego Pacheco barely landed any punches during the first four-plus round of his fight with Enrique Collazo on Saturday.

When Pacheco finally caught Collazo with a flush right hand, Collazo couldn’t take it. Pacheco dropped Collazo with 1:10 to go in the fifth round of their super middleweight match on the Canelo Alvarez-Gennadiy Golovkin undercard at T-Mobile Arena.

Collazo answered referee Celestino Ruiz’s count in time to continue, but he was still hurt and didn’t last much longer. Pacheco cracked him with two more right hands that eventually led Ruiz to halt their scheduled 10-round, 168-pound bout at 2:29 of the fifth round.

Puerto Rico’s Collazo (16-3-1, 11 KOs) represented a step up in competition for Los Angeles’ Pacheco (16-0, 13 KOs), a 21-year-old prospect who became the first opponent to stop him.

After four mostly mundane rounds, Pacheco finally began to time the cautious Collazo, who boxed almost exclusively off his back foot, in the fifth round.

A right uppercut by Pacheco connected barely 1:10 into the fifth round. Pacheco sent Collazo to the canvas approximately 40 seconds later.

Pacheco clipped Collazo with a right hand about 1:10 into the fourth round. Another right hand by Pacheco caused Collazo to hold him with just under 20 seconds on the clock in the fourth round.

Pacheco connected with a right hand a little less than two minutes into the third round, another three minutes of nondescript “action.”

After an utterly uneventful first round, Collazo and Pacheco spent most of the second round feinting and measuring each other, without throwing many punches. Neither Pacheco nor Collazo threw many punches during a dull first round that lacked action.

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