Castro's potential 'what he wants it to be,' says Sveum

CHICAGO -- The Cubs know that shortstop Starlin Castro has a bright future ahead of him. It's just that he continues to make some puzzling mistakes.

In the second inning of Saturday's game, he made an error on a routine grounder on a potential double-play ball and had a rough day at the plate, going hitless and seeing only 14 pitches in five at-bats.

It was a bad day, no doubt, and it seems like those bad days just leave everyone wanting more out of the 23-year-old.

"His potential is what he wants it to be, that's the bottom line with him," manager Dale Sveum said. "How good he wants to be, that's up to him -- the hard work and the concentration levels and being able to have all kinds of things in your toolbox as a shortstop, as well as a hitter."

Sveum has seen growth in Castro from last season to this season, especially when it comes to cutting down on mental lapses. Although that's a start, Castro is still making physical errors -- not just defensively -- at an alarming rate.

"Mentally, I think he's gotten a lot better, but physically and things like that, I think we're seeing a lot of the same stuff that we still need to get better at on a consistent daily basis -- the concentration of at-bats and defense and all that, too," Sveum said. "When you get to this level and you've played this much now, it's up to him how good he wants to be."