HBO Sports’ flagship boxing series returns with an action-packed card headlined by two of the sport’s fastest-rising stars when WORLD CHAMPIONSHIP BOXING: JULIO CESAR CHAVEZ JR. VS. MARCO ANTONIO RUBIO AND NONITO DONAIRE VS. WILFREDO VAZQUEZ JR. is seen live SATURDAY, FEB. 4 at 10:00 p.m. (ET)/7:00 p.m. (PT) from the Alamodome in San Antonio, exclusively on HBO. The HBO Sports team of Jim Lampley, Larry Merchant and Emanuel Steward will call all the action, which will be available in HDTV, closed-captioned for the hearing impaired and presented in Spanish on HBO Latino. After standout matches on HBO in 2011, Mexico’s Julio Cesar Chavez Jr. and Nonito Donaire of the Philippines begin 2012 against formidable opponents at a venue known for bringing out the best in fighters. The 12-round, 160-pound main event features Chavez Jr. (44-0-1, 31 KOs) defending his hard-earned middleweight title against an experienced challenger in fellow Mexican Marco Antonio Rubio (53-5-1, 46 KOs). Only 25, Chavez Jr. will have his work cut out for him in battling a prizefighter with 59 pro bouts under his belt. The co-feature is an intriguing 12-round junior featherweight title fight pitting fan favorite Nonito Donaire (27-1, 18 KOs) against the formidable Wilfredo Vazquez Jr. (21-1-1, 18 KOs) of Bayamon, Puerto Rico. Budding superstar Donaire, now residing in San Leandro, Cal., scored one of 2011’s most memorable victories when he knocked out Fernando Montiel last February. Now, the engaging 29-year-old, who last lost a pro fight in 2001, moves up in weight to the 122-pound division in hopes of adding a new title belt to his collection. Vazquez Jr., who hails from a boxing family, has other plans. The night of boxing programming kicks off at 9:45 p.m. ET/6:45 PT when an all-new edition of “2 Days: Portrait of a Fighter” debuts. The Feb. 4 installment of this revealing and intimate look at a 48-hour span in the life of a boxer in the lead-up to one of his fights will focus on lightweight Brandon Rios of Oxnard, CA. The feature is approximately 15 minutes.