Sisk (elbow) began a throwing progression July 18, MLB.com reports.
The Pirates haven't provided word on when Sisk will be ready to begin a rehab assignment, but that could happen soon if he's experienced no setbacks while ramping up his throwing. Before hitting the shelf July 4 due to left elbow inflammation, Sisk turned in a 2.23 ERA, 1.18 WHIP and 43:13 K:BB in 36.1 innings out of the Pittsburgh bullpen.