Of the defensive data beginning to trickle out of Statcast, one piece that has been particularly interesting to me is that the starting depth of center fielders seems to have a pretty significant impact on their defensive performance.
New Cardinal Dexter Fowler is one of the most interesting test cases.
Fowler has been a poor center fielder by metrics like UZR and DRS throughout his career. In 2015 - the first year for which we have Statcast data - he played the shallowest center field in the National League. In 2016, Fowler moved his average positioning back 17 feet - the biggest change of any outfielder. He posted the best season of his career by UZR and DRS.
Fowler is not the only outfielder for whom starting position seems to be a major factor in defensive performance. Kevin Kiermaier - the best CF defender - also happens to play the deepest. Then there's the case of Andrew McCutchen. The Pirates pulled a reverse-Fowler with McCutchen last season, moving him in to the shallowest starting position in the league. His defensive performance cratered.
One of the most exciting components of Statcast is the promise of allowing us to divide up the elements of defense and better evaluate things like first-step speed, full-sprint speed, route efficiency and the other elements we have folded into "range." But it looks like the simple element of starting position depth may have a bigger impact on range than we anticipated.
UZR divides its measure of an outfielder into three areas: Range Runs, Error Runs and Arm. For his career, Fowler has been 15 runs below average in arm, five runs below average in errors, and a whopping 43 runs below average in range.
Last season, after moving his positioning back, Fowler improved his Range Runs all the way to a positive 2.0.
The giant asterisk on all of this is of course that we aren't supposed to take a single season's defensive stats on face-value. If you choose to believe Fowler's positioning improved his defense, you are buying into a narrative more so than hard stats.
That said, the promise of Statcast is to move us from some of these more broad measurements like UZR to a point where we can measure actual tools, and see changes on a much more micro-scale. I'm fairly convinced that much of what we attributed to "range" for center fielders was influenced by starting position, and therefore Fowler may well be able to sustain something closer to his 2016 defensive value as a Cardinal.