"I think 'Welly' will say it wasn't one of his better games to receive the ball," Cubs manager Dale Sveum said on Saturday. "Sometimes you do struggle with certain pitchers and you lose concentration. He's still developing into what [coach Mike] Borzello wants him to do, so I think he kind of reverts back sometimes, maybe when the game starts speeding up and you've had to catch 200 pitches.
"We got a grip on it, and he knows what he was doing, and we know what he was doing," Sveum said of Castillo. "It's not a big concern. It's a little more of getting comfortable and doing what's called a quarter-turn with the hand, and do it on a consistent basis."
Sveum compared it to a hitter who is constantly working on his mechanics in the cage, then reverts back to bad habits when he gets in the batter's box.
"We have to stay on him to make sure he doesn't revert back to old habits," Sveum said. "Sometimes in the course of the game, it speeds up and you're worried about calling the game, and you revert back to what's comfortable for you, and it's not necessarily the right thing."