As any Orioles fan can tell you, Nick Markakis has an excellent outfield arm. But how does his arm rank compared to the rest of the league? And how much does arm matter when evaluating defense? FanGraphs does the heavy lifting, and Markakis comes out as the fourth best outfield arm in all of baseball. Before we get too carried away though, the best arm is worth about 15 runs more than the very worst arm per season. So while it does have some value, range and offense are clearly more important factors.
UPDATE: FanGraphs lives up to its name and delivers an outstanding pictorial depiction of the distribution of outfield talent along three dimensions: offense, range and throwing arm. The most amazing thing might be this nugget: "A league average bat who is an elite runner and thrower is about equal in value to a Ryan Braun type of hitter."