Bart left Sunday's game against Atlanta due to a left thumb injury, Alex Stumpf of MLB.com reports.
Bart was pulled before the start of the second inning Sunday, with Yasmani Grandal taking over behind the plate. The severity of the injury is not yet known, but Bart is being evaluated by medical staff, per Noah Hiles of the Pittsburgh Post-Gazette. Bart has gone 9-for-28 with one home run and four RBI in May.