Bart (thumb) will begin a rehab assignment with Triple-A Indianapolis on Friday, Alex Stumpf of MLB.com reports.
Bart will see game action for the first time since being placed on the 10-day IL on May 28, a significant step forward in his recovery from a Grade 1 thumb sprain on his glove hand. Once he's cleared to rejoin the Pirates, Bart should push Jason Delay out of the catching mix.