After losing his world championship to "The Answer," one question looms for Hilo's BJ Penn: When is the rematch?

Frankie "The Answer" Edgar upset Penn to win the UFC lightweight world title in the co-main event of the "UFC 112: Invincible" mixed martial arts event on Saturday at Abu Dhabi, United Arab Emirates.

At the post-fight press conference, UFC president Dana White said Penn will receive a chance to regain the title, although he is not sure when.

"I haven't talked to BJ," White said. "We'll have to see what happens to BJ. I'm sure there'll be a rematch. BJ is one of the best (155) pounders in the world. I don't think he's going to go anywhere."

White hinted that Edgar's first title defense could be against Gray Maynard, with a rematch against Penn to follow later in the year.

"Maybe Frankie defends his title (against Maynard), and then there'll be a rematch," White said. "I don't know. We'll see what happens."

Penn did not attend the post-fight press conference.

In a video blog on www.bjpenn.com, Penn said: "I want to congratulate Frankie Edgar. He fought a great fight tonight. Congratulations. He's the new champ."

Edgar stunned the MMA world with his unanimous decision victory over Penn. Some online gambling sites were listing Penn as an 8-to-1 favorite.

"Maybe one of the biggest upsets in UFC history," White said.

The five-round bout was mostly about stand-up punching. Edgar used an effective stick-and-move technique to stymie Penn.

"With BJ, his timing's great so you can't just go in without something behind it," Edgar said. "Movement was key in that fight."

White said of the fight's style: "I'm surprised. That's why I said BJ Penn fought Frankie Edgar's fight. I was expecting BJ to shoot at some point in that fight and try to take him down and submit him."

Penn, who is a former jiu-jitsu world champion, did not attempt any takedowns during the bout, even after his corner encouraged him to do so after the third round. Edgar got two takedowns, but Penn quickly scrambled to his feet after each one.

Edgar noted that his constant side-to-side movement throughout the bout may have played a role.

"Was I expecting (Penn) to shoot? He could have," Edgar said. "But I think the movement was a little hard for him to shoot on."

All three judges scored the bout in favor of Edgar, including one judge who scored it 50-45, meaning all five rounds went to Edgar.

"I thought the fight was way closer than that," White said. "I honestly didn't know who was going to win that fight and I thought it could have gone either way."

Fightmetric.com, a Web site that analyzes statistics from MMA bouts, interestingly had Penn winning the bout by a 49-47 score. According to the site, Penn landed 72 strikes at a 27.4 percent success rate, while Edgar landed 63 strikes at a 25.8 percent success rate.

In any case, Penn dropped to 15-6-1, and it was his first loss in the lightweight (155 pounds) division since 2002. Edgar improved to 12-1.

Penn departed Abu Dhabi immediately after the bout, but is not expected to return to Hilo for a few days. He will make stops in New York and California to promote his new book, "Why I Fight."

WHITE NOT PLEASED WITH SILVA'S WIN

The co-main event on Saturday featured Anderson Silva successfully defending his middleweight world championship against fellow Brazilian Demian Maia.

Silva won by unanimous decision, but it was his antics in the Octagon that had UFC president White fuming at the post-fight press conference.

"I don't think I've ever been more embarrassed in 10 years of being in the business," White said. "It's the first time I've ever walked out of a main event."

In between occasional punches and kicks, Silva danced around the cage for all five rounds, often clowning with Maia and the referee. The crowd was laughing for the first two rounds, but by the fifth round, Silva was getting booed.

"The way I feel, my mission was completed," Silva said. "I came in and dominated the fight and did what I had to do."