Parra has faced 37 batters as a Red.
10 were lefty hitters and Parra did well against them. OPS against of .650.
27 were righty hitters. OPS against him of 1.442.
Parra was a starting pitcher, so the tendency may be to leave him out there to pitch longer stints. I've seen enough of him and his stats to be opposed.
But he does have good stats as a lefty reliever facing lefty hitters over 2012 and the beginning of 2013. LOOGY. Period. It has a chance to work.