Originally Posted by TheVulture
Seems like if WAR is actually measuring relative value of a player to a replacement specifically at his position, the relative value would have to be based on the average or median of production at that position, and therefore the net sum of all WARs would be zero or close to it.
The "replacement level player" isn't the average player at his position, since the assumption is that a team doesn't have a league average player just sitting waiting on the bench or in AAA. An average player, of course, is actually quite valuable--he's better than half the league. For that reason, "replacement level" is kind of a fringe bench/AAAA player.