What is W.A.R. put simply?
WAR stands for Wins Above Replacement. In other words, how much better or worse is the player you are looking at, than the average replacement player available either FA or from the Minors.
If a MLB player was average at his position in every way possible, he would have 0.0 WAR. A team full of Mr. Average at every position (where everyone puts up 0.0 WAR), is predicted to win roughly 48 games out of a 162 game season. Or 48-114 in W-L terms.
So, let’s take last year’s MVPs. Bellinger and Trout. Cody put up a total of 9.0 WAR, and Trout put up a total of 8.3 WAR. This means that a completely average team with 2019 Bellinger would win about 57 games. If you added Trout to this average and Bellinger team, they would win about 65 games.
So now you see the game Baseball Operations plays. How can we put as much WAR into a 26 man roster possible?
What goes in to calculating WAR?
The first thing you need to understand, is that WAR is calculated different for every position. Each position player has one formula, and pitchers have another. This is because players can only control their own play. An OF like Bellinger can only change the game when the ball comes to him or at the plate. So they say that they want Belli in the OF because of his shoulder. But it seems more likely that they noticed he adds more value in the outfield. (He had the 3rd best defensive OF rating of 2019 behind Robles, and Cain.)
Whereas perennial MVP Trout is the best bat in baseball and could win without playing Defense at all.
And each position player is then graded differently based on the difficulty of the position, and the availability of replacements. Here’s the actual equation for calculating position players’ WARs.
This looks more complicated than it is. All this really calculates is how above average a player is (in their league, AL or NL) at Batting, Base-running, and Fielding. Batting and base-running is universal (once park factor is considered). But fielding value is hard to peg. Each position has different roles to fill, as well as an inherent difficulty. So when you see “Positional Adjustment”, the is what they mean. Here’s some older Fangraph’s adjustments:
So the 2 hardest positions to replace defensively are Catcher and SS. Followed by a 3-way tie for third with 2B, 3B, and CF.
(For you Dodger fans, Seager and Smith are both rated well above average defensively.)
And the top 3 easiest positions to replace defensively are (not counting DH, duh) 1B, LF, and RF. (See how Bellinger moved from 1st to RF/CF and became an MVP?)