The rookie shortstop was in the No. 2 spot in the lineup for the second game of the Cubs' Interleague series against the Rangers. The team is 4-0 when Castro bats second.
"He's been consistent," Lou Piniella said of Castro, who was batting .365 and has reached base via a hit, walk or error in his first 14 games. Castro hit his second career homer in the third inning.
Castro is the youngest player in the Major Leagues, and obviously, the youngest shortstop. Rangers shortstop Elvis Andrus is second youngest at 21 years, 268 days.
On Friday, Castro was obviously upset with himself when he lined out to right field for the second out of the ninth inning in Chicago's 2-1 loss.
"The last two games, I've watched in the ninth inning -- he's made a couple outs and he's not happy with himself," Piniella said of Castro. "That's a nice sign. He competes. The kid competes. I'm impressed with him."
"To be so young, he still keeps the ball in the middle of the field," Rangers manager Ron Washington said of Castro. "Usually those young guys come up here and they're wailing. He keeps the ball in the middle of the field."
Ramirez did not play Friday because of a sore left thumb that's been nagging him.
"He says he can [be the designated hitter]," Piniella said. "We've got him in there as the DH, and let's hope he swings the bat."