Pressly didn't pitch Tuesday due to an undisclosed ailment, Brian McTaggart of MLB.com reports.
Pressly was scheduled to throw Tuesday, but manager Dusty Baker revealed that he was unable to do so because of an undisclosed ailment. The nature and severity of the issue are unclear, as is whether or not his availability for Opening Day will be affected. The Astros are scheduled to begin the regular season against the Mariners on July 24.