MANILA, Philippines -- Former President Joseph Estrada vowed to deliver the knockout punch on boxing superstar Manny Pacquiao's president of choice.

Pacquiao earlier promised to campaign for Sen. Manuel Villar of the Nacionalista Party, who, together with Senator Benigno ?Noynoy? Aquino III, leads Estrada in recent surveys of candidates in the May 10 presidential election.

Estrada downplayed the impact of a Pacquiao endorsement of Villar, saying the boxer himself failed to win in the 2007 congressional race.

?He campaigned for himself and what happened?? he asked in Filipino in a phone interview with the Philippine Daily Inquirer.

Estrada went on citing the case of Ali Atienza, who got the support of Pacquiao in the 2007 mayoral race in Manila but still lost.

?He (Villar) might end up like him (Atienza),? he warned.

There was a tinge of bitterness in Estrada?s pronouncement, probably because he, too, once tried to enlist the support of Pacquiao, currently regarded as the best boxer on the planet.

Pacquiao then was still with the administration, ardently defending President Gloria Macapagal-Arroyo against her political detractors. But for the upcoming elections, he opted to go for the billionaire Villar.

Still, Estrada said the boxing fan in him did not miss what could be Pacquiao?s penultimate bout before hanging up his gloves.

The former president said he was glued to the TV in his San Juan residence, much like millions of Filipinos who saw the fight in a variety of venues: barangay halls, basketball courts, restaurants, and movie houses.

And probably like the rest of Filipino fans, Estrada felt shortchanged in terms of action, mainly because of the reluctance of Pacquiao?s opponent to engage.

?There was nothing exciting in the fight. There was no knockout. The opponent didn?t want to fight. He was all defense,? Estrada said.

He said there might have been a KO, most likely in favor of Pacquiao, if Ghanian Joshua Clottey was a bit more daring and decided to come out of his defensive shell.

Pacquiao?s boxing at the $1.2-billion Dallas Cowboys Stadium in Arlington, Texas was so dominating that Clottey won only a single round in two of the three judges? scorecards.

After the elections less than two months from now, Pacquiao is eyeing a final bout against American Floyd Mayweather Jr.