Pennington (undisclosed) has been placed on the 7-day injured list, Conor Foley of The Times-Tribune reports.
The specifics of the injury weren't disclosed, but Pennington apparently tweaked something while taking a swing on a home run and looked uncomfortable running the bases a few days ago. The 34-year-old was hitting just .196 in 92 at-bats for the RailRiders.