"Every year I want to be better," Castro said on Friday at the Cubs Convention. "Every year, I work hard to be better than I was the year before. That's why I'm working now; that's why I'm not going to the World Baseball Classic. I won't play for the Dominican because it's more important for me to be ready for the [Cubs]. I want to help the [Cubs]."
Moises Alou, who is involved in the selection of the Dominican roster, had asked Castro during the season about playing in the Classic.
"I don't want to be on the bench," Castro said. "Jose Reyes is there, and I have respect for him, and I'd be on the bench. It's better for me to be working and play every day in Spring Training. If I go, I'd play one day, two days a week. I don't want that. I want to work."
Castro said it was difficult to say no.
"It's one of my goals to play for my country, and it's tough for me [to say no]," Castro said. "But it's not the last one. I know I'll be there."
Cubs outfielder Alfonso Soriano also said no to Alou because the veteran outfielder needs more time to prepare in Spring Training for the season.
"Moises called, but I felt it was better for me to be with the Cubs," said Soriano.