Parnell had a rough weekend against the Pittsburgh Pirates, suffering two losses.
In 10 relief appearances since July 22, Parnell is 0-3 with a 14.14 ERA and .429 opponent batting average.
Parnell's difficulties are a reminder that not every pitcher has a smooth return from Tommy John surgery. Parnell had the procedure on April 8, 2014.
There has been no particular setback prompting Parnell to land on the DL. Instead, Parnell has been deemed to be suffering from fatigue.