"Last year, I told him, 'Hey, you're my favorite player,'" Castro said.
Tejada and Castro, both from the Dominican Republic, had a chance to chat Saturday prior to the Cubs-Giants game.
"He asked me a lot of questions about the game, how he could be better," Tejada said. "I'd love to help him."
It's not the first time a young shortstop has reached out to Tejada. Hanley Ramirez and Jose Iglesias also have asked for advice.
"It makes me feel good and proud of myself when you see all those young guys who can be superstars of the future and they want to get information," Tejada said.
Tejada, 36, told Castro he'd give him a video about defense.
"I want to see how he plays," Castro said.
"He's asked me how to stay in the big leagues for a long time," Tejada said. "He's a really smart kid. I was the same -- when I was young, I asked a lot of questions. Because in this game, you never stop learning. That's probably why he's like that.
"What I like about him is his energy," Tejada said. "He can play defense, he can hit -- I think the best part about him is his hitting. I think he's going to be the guy of the future on that team."
Entering Saturday, Castro, 21, was batting .588 (10-for-17) in his last four games after going 2-for-25 in his previous six. His 52 hits this season rank tied for second in the National League and are third most in the Majors.
Tejada is right. Castro can hit. Thanks to Tejada, Castro may become a better defensive player.
"He's a good person, too," Castro said of the veteran.