MEMPHIS, Tenn. -- Manny Pacquiao defended his IBF junior featherweight championship with a powerful second-round knockout of Jorge Julio on Saturday night as part of the undercard of Mike Tyson's heavyweight title fight with Lennox Lewis.

In his first fight in eight months since an ugly draw with Agapito Sanchez in San Francisco, Pacquiao used a fierce attack to overwhelm Julio, a former WBA bantamweight champion making just his third appearance at 122 pounds.

Pacquiao floored Julio twice in the first three minutes, and another flurry sent him sprawling against the ropes 1:09 into the second round, ending the fight. Pacquiao leapt wildly into the air, then express his desire to unify the junior featherweight titles.

``I hope that now, people will start to respect me a little more,'' Pacquiao said. ``The plan was to come out and let him feel my power early. I knew after the first knockdown that it was a matter of time.

``I didn't think it would be that easy.''

Earlier, former WBA super featherweight champion Joel Casamayor stopped Juan Jose Arias in the eighth round.

Casamayor (27-1, 17 knockouts) controlled the action with the energetic but raw Arias (33-3-1), who was staggered in the fourth, then knocked to his knees in the fifth.

Casamayor, the Cuban Olympic champion who defected in 1996, was penalized for low blows in the sixth, but he knocked down Arias again in the eighth before Arias' corner threw in the towel.

Casamayor lost his title in January in a controversial decision to Acelino Freitas. No rematch has been set, but Casamayor said his true desire is to fight Floyd Mayweather for the WBC title.

``Freitas is afraid to give me a rematch,'' Casamayor said.

The Pyramid was mostly empty until the final bout of the eight-match undercard, with few of the hundreds of celebrities who are expected for the main event there early.