David Diaz, 31-1-1, of Chicago will challenge all-action champion Jose Armando Santa Cruz, 23-1, of Lincoln Heights, Calif. on the Hasim Rahman vs. Oleg Maskaev PPV championship fight card on August 12 at the Thomas and Mack Center in Las Vegas. Bob Arum of Top Rank made the announcement today. Santa Cruz, trained by Rudy Hernandez, is the WBC interim lightweight champion and he will defend that title against Diaz.  Diaz is the holder of the IBA lightweight title belt. Santa Cruz is having a sensational 2006 with wins over Michael Lozado (NABF title fight), Edner Cherry (NABF 'Fight of the Year') and Chikashi Inada (WBC Interim Lightweight Championship).  Santa Cruz is an aggressive, non-stop hard puncher who fires from many angles. Here is how the Rahman v Maskaev PPV undercard is shaping up for August 12.