Timothy Bradley continues to throw barbs into Manny Pacquiao ahead of their upcoming rematch at the MGM Grand Garden Arena in Las Vegas.

Bradley said in an interview on Thursday that Pacquiao's lengthy career has been taking its toll on the Filipino boxing icon - both physically and mentally.

The reigning WBO welterweight champion pointed out that Pacquiao has already lost fire and motivation after going through more than 60 fights with most of those fights against top-tier opponents.

"I think he may lack fire," Bradley said. "His motivation is not there. He's been at the top for a very long time. He has over 60 fights with all the best. He's 36 years old. Maybe this is one fight too late for him."

Bradley, who is coming off convincing wins against Ruslan Provodnikov and Timothy Bradley last year, won against Pacquiao in their first showdown in June 2012, but his victory was tainted by controversy.

The 30-year-old champion run away with a split decision win to take Pacquiao's WBO welterweight title, but most analysts and fight fans are convinced that Pacquiao was the clear winner.

Pacquiao, for his part, is not thinking about the result of their first fight anymore. While he knows that he clearly won against Bradley during their first showdown, Pacquiao said that losing is part of the sport.

"In this sport, sometimes you're on the winner's side, sometimes you're on the loser's side, so you have to prepare for that," Pacquiao said. "I never complain. In boxing, it's part of the sport. If you don't want to lose, then don't fight."

The former pound-for-pound king wants to score a convincing win against Bradley. Pacquiao wants a knockout win to prove that he still has the killer instinct that he was known for, but he insisted that he won't force a knockout.

The 35-year-old champion said that he learned a lot from his sixth-round knockout loss to Juan Manuel Marquez in December 2012, saying that he became careless because he was looking to finish off his Mexican rival quickly.

"If he didn't get me in six rounds, by seven rounds I could have finished him," Pacquiao said. "But by being careless, that's what happened."