Las Vegas, Nevada --- (L-R)  Undefeated WBC Middleweight Champion Julio Cesar Chavez Jr.  and two-division world champion Sergio Martinez pose during the   press conference in Las Vegas announcing their Mexican Independence Day Middleweight championship battle. Promoted by Top Rank, Zanfer Promotions and DiBella Entertainment, in association with Wynn Las Vegas,At&T and Tecate, Chavez Jr. vs Martinez will take place Saturday, September 15 at Thomas & Mack Center in Las Vegas, live on HBO Pay Per View. Photos by Chris Farina/Top Rank.