I have been in PB since the beginning and have done this perhaps a dozen times over many teams/seasons. I don't have time to look for specific instances but my recollection is that sometimes they do reasonably well (ie 4-5 innings no runs). Other times they have been hit hard (7-8 runns in 1-2 inn). It seems unpredictable. My advice would be to avoid it (especially in the playoffs) unless there is not a good starter available. However if you are a heavy underdog for the game in question what do you have to lose?