On Wednesday, he was active in a Minor League game, batting every inning.
"I hit a double, scored from second to home, hit a triple, ran the bases pretty good," Castro said Thursday.
Is he 100 percent healthy?
"Yeah," Castro said. "I don't feel anything. I moved on defense yesterday, took a lot of ground balls, moving quick, feel pretty good."
"He's checking all the boxes and we feel pretty good about it," Cubs general manager Jed Hoyer said of Castro.
Opening Day is Monday.
"I've got to be ready," Castro said. "No more time. No more Minor Leagues. I bat every time -- four every day, five at-bats every day. No more Minor Leagues. The Show is coming."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.