Cubs manager Mike Quade was disappointed after looking into Starlin Castro's on-field preparedness during Sunday's 6-2 loss to the Cardinals. Quade decided to keep Castro out of the starting lineup on Monday, calling it a "mental day off." "I was really disappointed and surprised, very surprised," Quade said of Castro's actions on Sunday night. "But it's something from Day 1 focus-wise. It's something, to be honest with you, that he has to work on. With his talent, that's the toughest challenge for him. "It's simply not acceptable, not good. He feels terrible. I talked to him today, and we are giving him a day. After seeing last night, you have to make his concentration a priority. Getting him to concentrate pitch to pitch. He can do it, and we think he will. And we'll make sure that happens." Cameras showed Castro, 21, not paying attention and reaching into his pocket for sunflower seeds during pitches in the sixth inning against St. Louis.