Bieber (shoulder) will throw a side session off a mound Tuesday, Keegan Matheson of MLB.com reports.
Bieber hasn't pitched since Aug. 20 due to shoulder inflammation, and he'll have to build his arm back up before returning to game action. The right-hander will be up against the clock to make it back in time before the end of the regular season. Bieber has made just 11 starts this season, posting a 4.37 ERA, 1.42 WHIP and 44:24 K:BB across 55.2 innings.