When lightweight champ Juan Manuel Marquez and former titleholder Juan Diaz meet July 31 at Mandalay Bay in Las Vegas in a rematch of the 2009 fight of the year, they will have a strong supporting cast on the undercard. Golden Boy Promotions CEO Richard Schaefer, who vowed when the fight was announced in May to deliver a worthy undercard for the $49.95 HBO PPV show, believes he has done that with the addition Wednesday of a junior welterweight fight between Joel Casamayor and Robert Guerrero, both former two-division titleholders. Casamayor-Guerrero, a scheduled 10-rounder at a maximum contract weight of 139 pounds, rounds out the four-fight telecast that will include Marquez-Diaz II, 2009 ESPN.com prospect of the year Daniel Jacobs facing Russia's Dmitry Pirog for a vacant middleweight title and a lightweight bout between former two-division titlist Jorge Linares and perennial contender Rocky Juarez. http://sports.espn.go.com/sports/boxing/news/story?id=5294212
