The team is holding him back purely as a precautionary measure, and Napoli said it was just a little sore and he didn't feel the need to push anything.
"There's no concern," manager Ron Washington said. "He's got some little nagging things, and we just want to make sure it doesn't turn into anything more. He's getting some at-bats -- it's not like he's falling behind. We just want to make sure that little nagging things don't turn into anything more than what they are."
Washington said Napoli, who came into camp with a high left ankle sprain, was scheduled to have the day off on Sunday but is now likely to play against the Indians.