Manny Pacquiao’s trainer says the bout against Timothy Bradley is a “must-win.” (Reuters/Las Vegas Sun/Steve Marcus)

Manny Pacquiao will step into the ring Saturday night in a rematch against Timothy Bradley and, this time, the controversy swirling about the fight is limited to concerns about Pacquiao’s future.

Will this fight be his last?

It’s been a hot topic since he lost to Juan Manuel Marquez in December 2012, but Pacquiao wasn’t touching the topic this week, saying, “My journey will continue.” This is, as Mitch Abramson of the New York Daily News writes, no simple WBO welterweight title bout. There’s much more to it than that.

It wasn’t that long ago that Pacquiao (55-5-2, 38 knockouts) ruled the sport, emerging as a mesmerizing ball of fire in the ring. He sang karaoke and charmed studio audiences from the couches of talk shows. From 2008-9, Pacquiao dominated Oscar De La Hoya, Ricky Hatton and Miguel Cotto to cement his status as a superstar. In May of 2010, he won a seat in the Philippines Congress. In 2012, Pacquiao was named the second-highest grossing athlete by Forbes, trailing only Tiger Woods. Because of his past success, his fight on Saturday will likely push him past $700 million in domestic PPV revenue (he’s currently at $658,886,350), making him only the second fighter in the history of the sport to do so. (The other is Floyd Mayweather Jr.)

But fortunes in boxing quickly change and Pacquiao’s bashing at the hands of Marquez, coupled with his controversial split decision loss (though most thought he won) to Bradley in June of 2012 has tainted the Pacquiao brand. When he traveled to Macao, China, and won a wide decision against Brandon Rios last November, the fight did only 475,000 pay-per-view buys, his lowest output since he drew 206,000 buys in 2008.

Pacquiao’s own trainer, Freddie Roach, called it a “must-win” for the 35-year-old boxer who hasn’t won by knockout in 4 1/2 years, raising questions about whether his ability or his appetite for the sport may be diminished. Pacquiao outpointed Brandon Rios last fall but has lost two of his last three fights. Naturally, in the run-up hype to the fight, Bradley (31-0 with 12 knockouts) seized upon all of that.

“When was the last time you saw him knock somebody out?” Bradley asked (via the Boston Herald). “He had a guy sitting in front of him — a tough guy [Rios] — and he couldn’t get rid of him. I think it was the last round he had Rios trapped in the corner and you saw Manny take his foot off the gas pedal and it was unbelievable to me.

“In our fight I had two wounded feet and he couldn’t take me out. Manny Pacquiao used to come in blazing and knock guys out. He didn’t mess around. Now it looks like he’s more compassionate towards his opponents and that’s not good for boxing.”

Pacquiao lost his welterweight title to Bradley in June 2012 when judges C.J. Ross and Duane Ford scored the fight 115-113 for Bradley. Both judges have retired and the Nevada State Athletic Commission appointed new officials for Saturday’s 9 p.m. rematch at the MGM Grand.