"He's done some good things this spring, and to be honest with you, I'm a little shocked. ... He's definitely looking like he's more comfortable, and the one thing we all noticed is it looks like he's going to be an exceptional fastball hitter. We're sitting around watching him with the breaking ball, and he's shown he can handle that. He's very aggressive. You can tell he's played a lot of baseball."

Walker said he has yet to make any adjustments to the rookie's swing and doesn't know if he will have to. "It's very different but workable. He has a forward press early on, almost [Alfonso] Soriano-like. For a thin guy, he has big-time power. The only time he really loses his mechanics is when he tries to do too much and he comes in and out of it pretty violently. He's a max-effort guy, and that might be something we try to calm down later. But right now, we're just letting him play. He's a unique guy, that's for sure. And he runs great, which is nice to see some more speed out there. There's some big decisions that are going to be made in this camp, and as far as I'm concerned, he's in the mix."