Marylou Whitney's Birdstone tuned up for the April 10 Blue Grass Stakes (gr. I) Monday morning, breezing an easy six furlongs in 1:15 2/5 at Keeneland, his first work since his fifth-place finish in the Lane's End Stakes (gr. II) March 20."He worked great," trainer Nick Zito said. "He's not a big horse, but his stride was incredible this morning. I was really happy with the way he went. Right now, we just want to take it step by step and day by day, and if he works good again next week, we'll stay here and run in the Blue Grass."The son of Grindstone will be attempting to put himself back in the Kentucky Derby (gr. I) picture after being considered one of the early favorites for the Run for the Roses. Prior to the Lane's End, in which Birdstone was stuck down on the inside over a freshly sealed racetrack, he easily captured a mile and 70-yard allowance race at Gulfstream in his 3-year-old debut. He had capped off his 2-year-old campaign with an impressive score in the Champagne Stakes (gr. I).Expected to face Birdstone in the Blue Grass are Preachinatthebar, Action the Day, Limehouse, Mustanfar, Gradepoint, and possibly Lion Heart, who worked five furlongs in 1:01 2/5 at Santa Anita Monday. A decision by Lion Heart's connections whether to run in the Blue Grass or Santa Anita Derby will be made today after trainer Patrick Biancone talks with the colt's owners, Michael Tabor and Derrick Smith. If no other speed horses enter the Blue Grass picture, Lion Heart would clearly be the only speed in the nine-furlong race, which normally is run over a track that favors frontrunners.Also working for the Blue Grass Monday was Gradepoint, who breezed a half in :50 1/5 at Churchill Downs for trainer Neil Howard. The son of A.P. Indy also is looking to rebound off a disappointing effort after finishing eighth in the Louisiana Derby (gr. II) as the 2-1 favorite.The Blue Grass lost its likely favorite, Eurosilver, when the son of Unbridled's Song came down with a throat or gland infection, which forced Zito to withdraw him from the race.Zito will run The Cliff's Edge, third in the Florida Derby (gr. I), in the Wood Memorial (gr. I) the same day. Florida Derby runner-up, Value Plus, who will be one of the favorites for the Wood, turned in a sharp five-furlong work in :59 at Palm Meadows training center Monday. It was the co-second fastest, with stablemate West Virginia, of 14 works at the distance.