Mike Dallas Jr. was unable to survive the first round in what proved to be the toughest bout of his boxing career.

Lucas Matthysee of Argentina landed a short, hard right to the side of Dallas' head, and the Bakersfield fighter crumpled to the canvas. No count was needed. The official time was 2:26 of the first round.

Matthysee retained the WBC interim super lightweight (140 pounds) championship.

The fight was part of a Showtime televised card from the Hard Rock Hotel and Casino in Las Vegas.

Dallas was on his feet and his eyes looked clear about a minute after he was KO'd. According to the Showtime announcers, Dallas was going to be examined by a doctor in his dressing room.

Matthysee improved to 33-2 with his 31st knockout. Dallas fell to 19-3-1.

Dallas came out quickly and threw many left jabs as he tried to be the aggressor.

Matthysee, who recorded his sixth straight knockout, threw some wild punches, with most of them missing. Matthysee appeared to land a couple of shots, but nothing appeared to land clean until the knockout punch.

The KO came quickly. Dallas threw another left jab, with Matthysee leaning back as the punch was short of the mark.

Matthysee then threw a short right that landed flush on the left side of Dallas’ face, ending the fight.

It was Dallas’ first fight since his father and former trainer, Mike Dallas Sr., died in November.

Matthysee’s win sets him up as the probable opponent for the winner of the Feb. 9 bout between Danny Garcia (25-0) and Zab Judah (42-7).

Before Saturday’s fight, it was reported by Showtime that Matthysee was accused by Dallas’ trainer Virgil Hunter of taking a substance that Matthysee’s cornermen said was Amino 4500.

Keith Kaiser, Nevada State Athletic Commission executive director, said the commission’s doctor spoke with Matthysee’s people and was satisfied with the explanation. Kaiser said both boxers would be tested for banned substances before and after the bout, which is standard procedure.