Lyles left Tuesday's game against the Twins due to cramping in his right side, Bill Brink of the Pittsburgh Post-Gazette reports.
Lyles said the removal was precautionary, so it doesn't appear as though his status for Opening Day will be threatened. If the issue turns out to be worse than expected, Lyles would be forced to drop out of the competition with Steven Brault and Nick Kingham for the fifth starter role.