Hughes was sent to be examined by a doctor on Tuesday, and Girardi said that he expects Hughes to miss "a few days."
"There's always a little bit of concern," Girardi said. "It's [his] upper back, so we'll see how he is in a couple of days. The good thing is, he was ahead of where he'd probably normally be at this time, so it helps."
Hughes, 26, was 16-13 with a 4.23 ERA in 32 starts last season. This promises to be an important year for the hurler, who can be eligible for free agency after the 2013 campaign.