Hartlieb was sent back to the Pirates' satellite camp in Altoona on Thursday, Rob Biertempfel of The Athletic reports.
Hartlieb was working at the team's major-league training site over the past few days, but he'll head to the alternate training site ahead of the regular season. The right-hander made 29 appearances for the Pirates last season, logging a 9.00 ERA and 38:18 K:BB over 35 innings.