Manny Pacquiao will have to hang up his gloves if he shows a less-than-stellar performance on his fight with the unbeaten Timothy Bradley on Saturday, his trainer Freddie Roach said.

Roach seemed determined to push Pacquiao to display his full strength and show that he is truly in a different league compared to the undefeated Bradley. He made it clear he does not want to see the Philippine boxing hero struggle against Bradley.

"Manny should eat (Bradley) up as he comes forward. I think Manny should look really good in this fight... If he looks bad, he retires. At least I'll tell him to. And he may be the first one who will listen to me" Roach said, according to a report by the Associated Press in The Washington Post.

Pacquiao, 33, is under the pressure of public expectation after his underappreciated victories over Shane Mosley and Juan Manuel Marquez.

The public missed his best form and attacks in his previous fights, but Pacquiao remains optimistic he learned valuable lessons from those.

The WBO welterweight champion relates the pressure he is feeling now to how he felt during his first match with Erik Morales in 2005.

"After the fight with Morales, our first fight, [I felt the pressure to look good]," Daily Mail reported.

On his insight regarding his fight with Morales, Pacman admitted a lapse in discretion.

"I think we underestimated Marquez, but we trained hard for that fight. The training was still the same," he said, noting, "I've been fighting with bigger guys and then I fight a guy who is the same size, so I kind of understimated [him]."

For his part, Bradley said he was ready for anything.

"I'm ready to shock the world. I'm ready to do anything I need to do to win. I'm ready to go to war," Bradley said.

Pacquiao (54-3-3, 38 KOs) and Bradley (28-0, 12 KOs) will face-off at the MGM Grand Garden Arena in Las Vegas, Nevada this weekend.

Meanwhile, American Idol runner-up Jessica Sanchez, will sing the American national anthem prior to the boxing match.

"Singing the American National Anthem @ the Pacquiao fight this Saturday in Vegas! I am sooooooooo ecstatic!! :)" the 16-year-old singer tweeted.