Las Vegas: Twenty-four years after first climbing into a professional boxing ring, Manny Pacquiao will attempt to defy the march of time here Saturday when he battles undefeated American Keith Thurman for the WBA welterweight crown. The 40-year-old Filipino icon clashes with Thurman at the MGM Grand in Las Vegas in what is arguably his most challenging assignment since losing to Floyd Mayweather in 2015’s money-spinning “Fight of the Century”. Pacquiao, who has managed to successfully juggle a political career in the Philippines while continuing to box at a high level, looked sharp in his last outing in January, a unanimous decision against Adrien Broner. Also Read – Andy Murray to make Grand Slam return at Australian OpenBut the eight-division world champion is facing an altogether higher-calibre opponent in the shape of Thurman, renowned as one of the hardest punchers in the welterweight division with 22 knockouts in 30 fights. Thurman, who at 30 years old is a full decade younger than Pacquiao, sees Saturday as an attempt to build his legacy, and has bluntly vowed to send the Filipino into retirement. “This is a once in a lifetime opportunity to destroy a legend,” Thurman declared, placing Pacquiao in the boxing pantheon alongside some of the sport’s greatest practitioners. Also Read – Fast bowler Behrendorff to undergo spinal surgery”It’s as if I’m fighting Sugar Ray Robinson or Roberto Duran,” Thurman said. “This is Manny Pacquiao. It’s a tremendous feeling, and it’s going to feel even greater when my hand is raised at the end of the night.” Pacquiao (61-7-2, 39 knockouts) has shrugged off Thurman’s blood-curdling pledges of destruction, insisting he harbours no animosity towards the brash American. “For me nothing is personal,” Pacquiao said. “Our job is to fight. He has to prove something, and I have to prove something. It’s easy to say things. But it’s not so easy to do it in the ring.” Pacquiao’s preparations for the fight have followed a familiar routine. After spending the first part of his training camp in the Philippines, he relocated to Los Angeles to work under the guidance of long-time trainer Freddie Roach at his Wild Card gym in Hollywood. Roach maintains that Pacquiao has shown no sign of decline during gruelling sparring, and is confident that his speed and mobility will cause problems for the naturally bigger Thurman.