LOS ANGELES – Ronny Rios has had a tendency in his young career to lose his cool when things get hot in the ring, which he acknowledges.

Thus, one of his goals going into his fight against veteran Leivi Brea in the “Fight Night Club” main event Thursday night at Club Nokia in Los Angeles was to be patient.

He was. Rios calmly picked apart his Dominican opponent before finally breaking him down, putting Brea down twice and ending his night with vicious body shots in the fourth round of a scheduled six-round junior lightweight bout. The fight was stopped at 2:59.

Rios (12-0, 6 knockouts) is now 4-0 in “Fight Night Club” bouts at the downtown L.A. night club.

“I didn’t want to do anything dumb and get caught,” Rios said. “ÔǪ I wanted to take my time and break him down. I’m not a devastating puncher. I need a few rounds to break my opponents down. And that’s what happened.”

Rios fought carefully in the opening round as he tried to figure out Brea (17-9-3, 9 KOs), a solid boxer and good athlete who moves well in the ring.

The victor picked up the pace as the progressed, however, stalking his foe and landing more and more consistently. In turn, as he took more punishment, Brea was less and less willing to engage Rios as the fight went on.

Rios hit Brea with what referee Jose Cobian ruled was a low blow in the third round, which halted the fight for several minutes. Still, Rios, who believed Brea was faking, targeted his body.

“Why go outside the game plan if it's working?” he said.

Indeed. Rios picked up the fourth round where he left off in the third. He put a retreating Brea down with the two legal body blows, sending the beaten man to his knees and ending the fight.

Rios will now move up to eight-round fights, said his trainer, Hector Lopez.

“Now I have to really watch my diet, watch my cardio,” he said. “I have to do my weight conditioning. I don’t want to fall behind like some other prospects. ÔǪ It gives me more motivation to fight eight rounds now.

“I’m patient, though. I’m only 20. I want to develop my full strength. There’s no rush.”

Rios’ older brother, Salvador Rios, also had a successful night.

The elder Rios, making his pro debut, didn’t fight for the first time until he was 17 and had fought sporadically as an amateur since. Instead, he went to school and worked to help his mother with household bills.

However, watching Ronny fight, he got the bug to give it a serious try. The result was impressive: He stopped overmatched Stephen Rubalcava (0-2) of Lindsay, Calif., at 1:35 of the second round of a scheduled four-round welterweight bout.

Rios, 23, demonstrated unusual discipline for someone making his debut. He patiently looked for openings and landed hard, accurate punches. His body attack was particularly effective.

The fight was stopped because Rubalcava was taking considerable punishment without throwing back with any effectiveness.

Was he nervous?

“No, not really,” he said. “I was a few weeks ago. But as the fight got closer, it went away.”

Ronny, who is very close to his brother, was nervous for him.

“I was so nervous,” he said. “My heart was pumping. After he won, I felt like I won. I felt like, 'OK, I don't have to fight any more (tonight).”

Also on the undercard, talented San Diego prospect Antonio Orozco (8-0, 5 KOs) walked away with another victory and a valuable learning experience.

Orozco’s opponent, Humberto Tapia, is one of those tough Mexican fighters who give hell to rising prospects but usually end up losing a decision. That was the case on Thursday, as Orozco outboxed Tapia to win a unanimous decision but had to work extremely hard.

Tapia (15-15-1, 8 KOs) is much better than the 3-9 record in his last 12 fights. He has been stopped only once.

Ghanaian prospect Bastie Samir (4-0, 4 KOs) stopped Jacob Alvarez (0-2) of Victor Valley, Calif., 2:37 into a scheduled four-round super middleweight bout.

And, in a wild slugfest, Jonathan Bobadilla (5-3) of Los Angeles outpointed Juan Figueroa (6-8-1, 3 KOs) of L.A. in a four-round junior welterweight bout. Figueroa was left with golf ball-sized bump on his forehead as a result of a head butt.