What exactly is this? In the glossary BP explains it as this...
Yet in the future PDTs they order the pitchers according to RAR...RAR, RAR2
Runs above replacement. A fielding statistic, where a replacement player is meant to be approximately equal to the lowest-ranking player at that position, fielding wise, in the majors. Average players at different positions have different RAR values, which depend on the defensive value of the position; an average shortstop has more RAR than an average left fielder.
Is this just the number of runs that particular pitcher is expected to save from being scored over a replacement player? If so, what factors go into determining this?