LAS VEGAS -- William Joppy wasted no time putting his name into the increasingly lucrative middleweight mix.

Joppy, hoping for a possible fight with Felix Trinidad, needed less than four full rounds Saturday night to stop an outclassed Jonathan Reid to retain the WBA middleweight title.

Fighting a night after Bernard Hopkins defended the IBF version of the 160-pound title just down the Las Vegas Strip, Joppy knocked Reid down twice before referee Joe Cortez stopped the fight at 2:43 of the fourth round.

"My goal tonight was to show Trinidad and Bernard Hopkins that I'm the best in the division," Joppy said.

It was hard to tell against Reid, who was undefeated in 27 fights but took the fight on only two weeks notice after Guillermo Jones pulled out because he was having trouble making weight.

The fight was on the undercard of the Trinidad-Fernando Vargas 154-pound unification bout at the Mandalay Bay hotel-casino.

Joppy, making the fifth defense of his title, punished Reid from the opening bell, landing big right hands behind an effective jab.

Joppy (32-1-1) put Reid down midway through the third round with a big right hand and flurry. Reid was up at the count of seven but was taking punishment in the corner when the bell sounded to end the round.

Cortez asked Reid if he wanted to continue, and he did, coming out in the fourth round to take even more punishment. He was being pounded on the ropes and went down once more as Cortez moved in to stop it.

"I made a big statement tonight," said Joppy, 159½, of Silver Spring, Md. "People are going to start realizing who I am."

Reid (27-1), 160, of Nashville, said he would have given a better performance if he had known of the fight earlier.

"I took the fight on short notice," Reid said. "If I had time to train I think it would have been a little better."

In another title fight, Ricardo Lopez of Mexico defended his IBF light flyweight title by stopping Ratanapol Vorapin of Thailand in the third round of a scheduled 12-round bout.

Lopez, fighting for the first time since winning the title 14 months ago, hurt Vorapin with a left hook in the third round and followed it with a flurry of head punches before referee Richard Steele stepped in and stopped the fight at 2:11 of the third round.

Ringside punching statistics showed Lopez outpunched Vorapin 31-1 in the third round.

Lopez, who made 21 defenses of his 105-pound title before moving up in weight, improved to 49-0-1. Vorapin fell to 38-6-1. Both fighters weighed 107½.

In another undercard fight, Christy Martin upped her record to 41-2-2 by stopping Sabrina Hall of Grafton, Ohio with a big right hand in the first round of their scheduled eight-round women's bout.

Martin dropped Hall with the punch midway through the round and the fight was stopped at 1:05 of the round as she wobbled to her feet.