Edgy MD wrote: WAR is the name of two different stats that profess to measure the same thing. They come from two different sources — Fangraphs and Baseball-reference — so they are distinguished colloquially as fWAR and bWAR. As both are proprietary, it's not altogether clear what differences they bring, but most (not all) prefer fWAR. They seem to have more sophisticated defensive measurements, though that doesn't necessarily mean more accurate. defense seems to be the big one. I believe Fangraphs uses FIP and BR uses RA/9 to calculate defensive value. There are other things, like positional weights and the like. I've heard, but haven't confirmed, that B-R weights what actually happened a little more, but that might just be a reflection on using runs allowed over FIP. The important thing to note is that they're counting estimates. They count up everything a player does on the field that contributes positively towards creating runs, subtract those things that contribute towards not scoring runs. You don't really need to over think it. There's definitely some work to be done, particularly on the positional adjustment side (an identical batting line for a SS And a RF will have very different WAR) but the concept is really just that. if you do things that typically contribute to run scoring, or run prevention, your WAR ticks up. so WAR/600PA is just projections. Like saying a guy at the ASB will hit 40 HR if he has 20.