Glendale,Calif.  --- Undefeated WBC World Middleweight Champion Julio Cesar Chavez Jr. swings a baseball bat at the heavy bag during a workout for his upcoming world championship doubleheader co-main event against #1 ranked Marco Antonio Rubio, Saturday,Feb. 4, televised live on HBO World Championship Boxing from the Alamodome in San Antonio,Texas. Promoted by Top Rank, in association with Zanfer Promotions, All Star Boxing and Tecate, Chavez Jr. takes on Marco Antonio Rubio and Nonito Donaire battles Wilfredo Vasquez Jr. in the other co-main event. --- Photos by Chris Farina/Top Rank.