By the turn of the 21st Century, Roy Jones Jr had seemingly achieved everything there was to in boxing.‘Captain Hook’ had beaten Bernard Hopkins for the IBF middleweight strap in 1993, before going on to reign supreme over the super middleweight and light heavyweight divisions.Jones Jr became a four-weight world champion by beating Ruiz for the WBA heavyweight titleGettyHe became the undisputed 175lbs king in 1999 with a points win over Reggie Johnson and defended his crown an astounding seven times.After blasting away Clinton Woods inside six rounds in 2002, Jones Jr made the bullish decision to jump up two weight classes to challenge John Ruiz for the WBA heavyweight title.It wasn’t the first time Jones Jr had attempted to cross over to boxing’s glamour division.In 1997, he gave up his WBC light heavyweight title in order to accept a $6million offer on the table to fight Mike Tyson conqueror Buster Douglas.However, Jones Jr’s father would ultimately convince his son to stay at his natural weight class over concerns he was “risking his life” by fighting the former undisputed heavyweight champion.There were no such qualms when Jones Jr signed to fight Ruiz six years later.By then, he was 34 years old and had grown into his frame more, although he was still incredibly light for the weight class.The day before the fight, Jones Jr weighed in at just 193lbs, a shade over the then-190lbs heavyweight limit.In stark contrast, Ruiz, who had boxed at heavyweight his entire career, tipped the scales at 226lbs – 33lbs more than his adversary.Despite this, Jones Jr was able to use his superior speed and ring craft to outwork and outbox Ruiz for the majority of the fight.Crawford, like Jones Jr, is moving up two weight classes to fight Canelo this weekendGettyJones Jr even rocked Ruiz in the fourth round with a perfectly timed right hand that left the champion hanging on for dear life.In the end, Jones Jr was handed a unanimous decision victory by margins of 116-112, 117-111, and 118-110 to become a four-weight world champion.Roy Jones Jr’s win is good news for Terence CrawfordTerence Crawford will be hoping to replicate Jones Jr’s successes this Saturday when he moves up two weight classes to box Canelo Alvarez for his undisputed super middleweight titles.‘Bud’, who only made his super welterweight debut last August after stints at lightweight, super lightweight and welterweight, will do so without the aid of a rehydration clause. If he can overcome the odds stacked against him, then the Omaha puncher will be crowned the first male three-weight undisputed champion of the four-belt era.Historical examples such as Jones Jr vs Ruiz, Michael Spinks vs Larry Holmes, and Henry Armstrong vs Barney Ross will serve as motivation ahead of fight night.