On Monday against the Marlins, Castro didn't make a good impression, committing three errors.
"He's going to be fine," Ramirez said Tuesday about the young Cubs shortstop. "He's got to forget last night. He's a good player. He had a really good at-bat against Nate [Robertson]. His approach is very good. He looks like a big leaguer at home plate. He's just got to keep doing what he's doing."
Ramirez talked to Castro before Monday's game and warned him that the game is the same, but "it's going to be faster."
"I think the pace of the players up here is so much faster," Ramirez said. "It happens like this [snapped fingers]. That was the difference I saw. You've just got to slow yourself down too. Sometimes, you try to speed it up, too, and it can get you."
Piniella wasn't too worried about the young shortstop, who was called up from Double-A Tennessee on Friday. Castro has already experienced the highs and lows of baseball. He set a Major League record with six RBIs in his debut game last Friday in Cincinnati, and then Monday made three miscues.
"We're going to grow with him," Piniella said.
The Cubs' coaches talked to Castro after the game about one of the plays in which he didn't hustle after a ball, which, coincidentally, was hit by Ramirez. Ramirez hustled to second on the ball. This has been a crash course on big league baseball.
"We've talked to him more than anything else about the tags at second base and how to properly get that glove down," Piniella said.
"He'll be fine," Piniella said. "Let's not get too occupied with this. He's got a learning curve ahead of him, and he's got the perfect guy in [Alan] Trammell and [Ivan] DeJesus to help him and a wonderful hitting coach [in Rudy Jaramillo]. He'll be taken care of the right way."
Alfonso Soriano has taken Castro under his wing, letting the young shortstop stay with him in his Chicago condo.
"We have to remember he's 20 years old," said Cubs player development director Oneri Fleita. "He's a tough kid. He's been battle tested. He'll bounce back."
Aramis Ramirez also talked to Castro after the game.
"I told him that last night, 'That's baseball,'" Ramirez said. "It can happen to anybody. I'm pretty sure if you watch baseball long enough, you'll see that happen to somebody else. It's not going to happen only to Starlin. He'll be a good player."