Bolton is expected to be promoted from Triple-A Indianapolis by the Pirates prior to Wednesday's game versus the Dodgers, Kevin Gorman of TribLive.com reports.
The Pirates haven't announced anything yet, but a jersey bearing Bolton's name was spotted in the team's clubhouse. Bolton has made a full-time move to relief this season and has thrived, holding a 2.38 ERA and 14:2 K:BB over 11.1 innings at Indianapolis. He will need to be added to the 40-man roster.