By Keith Idec

LAS VEGAS – Luis Arias easily handled what was supposed to be a step up in competition Saturday night.

Milwaukee’s Arias knocked down Arif Magomedov in the fifth round and quickly hurt him again to win by technical knockout at Mandalay Bay Events Center.

The 27-year-old Arias remained undefeated (18-0, 8 KOs, 1 NC). He also retained his USBA middleweight title in the first of three televised undercard fights prior to HBO Pay-Per-View’s telecast of the Andre Ward-Sergey Kovalev light heavyweight championship rematch.

Magomedov (18-2, 11 KOs), of Kizlyar, Russia, lost for the second time as a pro. Andrew Hernandez (19-5-1, 9 KOs, 1 NC) upset him by 10-round unanimous decision in their May 2015 fight in Las Vegas.

Arias hurt Magomedov with an overhand right with a little more than two minutes to go in the fifth round. Magomedov got up in time to beat referee Robert Byrd’s count, but Arias blasted him with another right hand that buckled Magomedov’s knees and made Byrd step in to stop the fight at 1:16 of the fifth round.

With about a minute to go in the fourth round, Byrd warned Arias for blatantly hitting Magomedov on a break. Byrd didn’t deduct a point, probably because Magomedov had hit Arias as well when Byrd had instructed them to break.

Arias landed several hard right hands in the third round. Magomedov held at times to recover and Byrd eventually warned him for clinching.

Arias and Magomedov both landed hard right hands in an exchange late in the second round.

Magomedov landed a solid right hand in the first round and followed it up with a combination. Arias had his moments in the first round as well, particularly with his overhand right and body blows.

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