Trainer Richard Mandella announced Tuesday that Gary Stevens will be aboard Halfbridled on Saturday when the 2-year-old filly champ makes her long-awaited 3-year-old debut in the $300,000 Santa Anita Oaks (gr. I).Stevens replaces the injured Julie Krone, who has ridden the daughter of Unbridled in all four of her starts."Gary is one of the greatest riders I've ever seen and has always been one of my favorites," Mandella said on a national teleconference. "I have no doubt he'll rise to the occasion. She's such a nice filly to ride, so I didn't have to look for anyone who has a particular style."Halfbridled, who tuned up for the Santa Anita Oaks with an easy half-mile breeze in :49 2/5 Tuesday, will then head to Keeneland for the April 3 Ashland Stakes (gr. I), after which a decision will be made whether to point for the Kentucky Oaks (gr. I) or the Kentucky Derby (gr. I)."Right now, I'm just focusing on the Santa Anita Oaks," Mandella said. "If she was to be as dominant in the next two races as she was last year, then it would be a serious question whether to try the colts or not. If she's not, then we'll definitely point for the Oaks."Halfbridled was originally scheduled to debut in the Las Virgenes Stakes (gr. I), but a cough kept her out of the race, and Mandella had to go to Plan B. "She didn't need much practice getting ready last year, and I don't feel she'll need much this year," Mandella said.