Manny Pacquaio will be forced to answer very difficult questions over whether he is still relevant as a top-level fighter if he fails to exact revenge on Timothy Bradley in Las Vegas on Saturday night, according to chief trainer Freddie Roach.
Pacquaio controversially lost on points to unbeaten Bradley in June 2012, a year which saw the eight-time world champion's career take a downturn following a stunning knockout defeat to long-time nemesis Juan Manuel Marquez.
Roach has helped Pacquiao respond from that shock to batter Brandon Rios for 12 rounds last November, but this weekend's rematch with Bradley will prove decisive in any plans to go on and look for a megafight with Floyd Mayweather or any other star in the sport, according to the Wild Card trainer.
He told The Telegraph: "This is a 'must-win' situation on Saturday night, and if we don't win this fight we have to consider maybe retirement.
"So this is a big, big fight for him. We are in a 'must-win' situation, it's as simple as that. Some people think we are all done and we have to prove that we are not."
The 35-year-old has age on his side in a bid to extend a magnificent 62-fight career in the paid ranks, although congressional commitments in his native Philippines coupled with a new-found devotion to religion have sparked have strengthened the view that he may call it quits before the end of 2014.
Bradley promises to provide a stern test of Pacquaio's desire to become WBO welterweight champion and a pound-for-pound contender, with the 30-year-old still unbeaten and looking to prove his points win back in 2012 was no fluke.