Liberatore (back) tossed a bullpen session Monday and said he felt good afterwards, Emily Waldon of The Athletic reports.
The 19-year-old was placed on the 7-day injured list at Low-A Bowling Green on Aug. 9 after developing back spasms. His ability to resume throwing without any reported discomfort leaves the door open for Liberatore to return to game action before the minor-league season ends.