Four former UFC champions will compete on Saturday night on the UFC 123 card at the Palace of Auburn Hills in Auburn Hills, Mich. In the featured attraction, light heavyweights Lyoto Machida and Quinton “Rampage” Jackson will square off, both hoping that a victory will move them closer to another crack at the UFC title. Meanwhile, a monumental trilogy four years in the making will add a chapter as former two-division titleholder B.J. Penn looks to erase the memory of successive setbacks when he returns to the welterweight division to settle the score with UFC Hall of Famer Matt Hughes. Here’s a breakdown of the UFC 123 card: Main bouts (on pay-per-view): Lyoto Machida (16-1) vs. Quinton “Rampage” Jackson (30-8) Both coming off harrowing losses, two of the top five light heavyweights in the game will clash in a thrilling headliner. It’s hard to believe that one year ago, UFC commentator Joe Rogan had welcomed us to the “Machida Era.” Undefeated at the time, the crafty karate master was coming off destructive back-to-back knockout wins over Thiago Silva and Rashad Evans, adding to an already stellar list of victims that included Tito Ortiz, Penn, Rich Franklin and Stephan Bonnar. A…