According to FanGraphs, Darwin Barney was an excellent defensive player in 2012. Barney, the everyday second baseman for the Chicago Cubs, was worth about 13 runs, or 1.3 wins above replacement, due to his defensive contributions at the pivot. This is a very good number.
According to Baseball-Reference, Darwin Barney was the most excellent defensive player in baseball in 2012, along with Brendan Ryan. In terms of wins above replacement, B-R had Barney at about three-and-a-half defensive WAR. This is a tremendous amount of value ascribed to a single player -- especially one who does not play shortstop. It can mean the difference between a good starter and an All-Star level of performance.
These two comparisons of value are just a bit different.
This is a symptom of a greater problem in sabermetric circles these days: can we trust single-season WAR values, when the defensive component of WAR is, let's just say "debatable"? For a while now, there's been a lot of discussion about how useful the defensive metrics that go into WAR are, especially on a year-by-year basis.
The most common refrain I hear is that the sample sizes used to judge a fielder's performance in a given year are simply too small to ascribe much real weight to these numbers. Nevertheless, a good (or bad) defensive season can mean a gigantic swing in wins above replacement. While the WAR metrics aren't used as catch-alls by everybody, when a player has a dramatic swing in perceived defensive value, it can show up in plenty of articles and analyses about how much value a player is worth, and how useful their performance has been / can be.
Perhaps what we need to do is *deep breath* rely less on the UZR / DRS / TZ / FRAA numbers, and more on a scouting perspective.