VORP can also be calculated for pitchers, as a measurement of the number of runs he has prevented from scoring that a replacement-level pitcher would have allowed. The concept is essentially the same as it was for hitters: using the player's playing time (in a pitcher's case, his innings pitched), determine how many runs a theoretical "replacement" would have given up in that playing time (at the most basic level, the replacement level is equal to 1 plus the league's average runs per game), and subtract from that number the amount "actually" allowed by the pitcher to arrive at VORP. As an aside, Run Average (RA9) is used as a measure of pitcher quality rather than Earned Run Average (ERA). ERA is heavily dependent on the concept of the error, which most sabermetricians have tried to shy away from because it is a scorer's opinion; also, we are trying to determine VORP in units of "runs", so a calculation that uses earned runs is not of very much use to us in this instance.