AS VEGAS – Shane Mosley has vowed to breathe new life into his career by making rising superstar Saul "Canelo” Alvarez pay for his over-confident approach to Saturday’s WBC super welterweight title showdown.Shane Mosley’s last big win came over Antonio Margarito. Mosley and Alvarez will square off on the undercard of the Floyd Mayweather vs. Miguel Cotto card at the MGM Grand Garden Arena in Las Vegas in a bout most see as being between two fighters heading in opposite directions.At 40, Mosley (46-7) might talk big about setting up rematches with marquee names Manny Pacquiao and Mayweather, yet the fighter has been in considerable decline and careening towards retirement. Alvarez (39-0-1), on the other hand, is tipped to become boxing’s next big thing and his advisors chose Mosley as a big-name stepping stone to greater things.Having been without a victory since his January 2009 triumph over Antonio Margarito, Mosley is seen as a heavy underdog against the undefeated 21-year-old Mexican. But the Californian is confident that his style and guile will pose problems for the younger man, especially if Alvarez has been struggling with motivation in training, as is rumored."I hear Canelo is not taking it that seriously, so that’s going to make for a great fight,” Mosley said. "I’m ready to fight. My mentality is to fight. It is up to people if they want to believe me when I say I am fitter and healthier than for my previous fights. I feel really confident that I can withstand whatever he throws at me.”Alvarez is seen as the emerging shining light of Oscar De La Hoya’s Golden Boy Promotions, and a victory would potentially put him in line to face either the winner of Andre Berto-Victor Ortiz or even Mayweather himself, before the end of the year.Defeat for Mosley would surely end any aspirations he has of rubbing shoulders with that kind of elite company again, and could prompt him to quit the sport entirely, ending a career that is clearly destined for the International Boxing Hall of Fame.Mosley is a six-time world champion and has such highlights on his record as a pair of wins over De La Hoya and Fernando Vargas, respectively. However, he testified to having injected himself with a banned substance ahead of his second fight with De La Hoya, and a career that began with 38 straight wins has tapered off considerably.Nowadays, he doesn’t even have his old belts to look back at with fondness, as those were taken by his ex-wife Jin as part of their divorce settlement.Some think it would take a miracle to get Mosley back into the frame for a major fight, but there is little question that a convincing win over Alvarez would do it. Canelo’s stock is high and beating him would not only show the world that Mosley’s fists still have some fire in them, but it would also clip the wings of a youngster on the rise."Winning a seventh world title would mean a lot,” Mosley said. "But just winning this title is going to mean even more because it puts me in line with the bigger fights that hopefully once I finish I can go ahead and fight the other two rematches.