A lot has changed for Manny Pacquiao in the past two years. Once considered the best pound-for-pound active boxer, along with Floyd Mayweather, Pac-Man has failed to perform like a top fighter. In June 2012, he lost a controversial decision to Timothy Bradley. Six months later, he was stunned by a sixth-round knock out by Juan Manuel Marquez.

Now, the boxer is looking to get back to the top of the sport. Pacquiao seeks his first win since 2011 when he faces Brandon Rios. The two boxers are set to square off in Mancua, China on November 23.

"I want to prove that I can still fight, and my boxing career is not done yet," Pacquiao told reporters in his final public appearance in the United States before he begins training in the Philippines.

Pacquiao’s bout with Rios could alter the course of his career. His trainer Freddie Roach has stated that he would advise Pacquiao to retire if he loses for a third straight time. Pacquiao, though, isn’t ready to call it quits and is doing what he can to prove he’s still a top fighter.

"Manny is a realist," Roach said. "If you don't think you can get knocked out in this sport, you picked the wrong sport. He knows it can happen. It happened twice before I met Manny Pacquiao. He showed me those tapes. He wasn't embarrassed by it. He knows it's part of life in boxing. That's why he deals with it so well. It doesn't bother him."

Rios, like Pac-Man, is also coming off a loss. He was defeated by Mike Alavarez in a unanimous decision in the first loss of his career. Despite Rios’s 31-1-1 career record, it would be a major upset if Pacquiao cannot get his first win in two years. The online betting Web site Boavada has set Pacquiao’s odds at minus-500, while Rios comes in at plus-350. Still, the 34-year-old doesn’t feel that he’s chosen an unworthy challenger.

"I didn't choose an easy opponent," Pacquiao said. "I didn't choose a tuneup fight. I chose to fight a good fighter. ... I love to fight. I love to throw a lot of punches. I have to make sure I'm in 100 percent condition and the killer instinct is still there."

Rios wasn’t Pacquiao’s first choice for his next fight. He looked to have a rematch with either Bradley or Marquez, but the two will face each other, instead. Pacquiao’s representatives have stated multiple times that they would like to make a fight with Mayweather a reality, but that doesn’t look like it will ever happen.

Before his loss to Bradley, Pacquiao had won 15 straight fights. He hadn’t been as dominant toward the end of that streak, though, failing to get a knockout in his last four bouts. Against Rios, Pacquiao is looking to show that he hasn't lost what made him an elite boxer.

"It's really important to win this fight," Pacquiao said. "Not just win, but to win convincingly, either knockout or decision, as long as the fans are satisfied."

Pacquiao will start training in October for six weeks. The fight will mark almost a year since he last stepped inside the ring.