Will Dexter Fowler's defense travel to St. Louis?

— -- One of the early storylines of the Chicago Cubs' championship season was the defensive improvement of Dexter Fowler. How did we know he was better? Metrics, of course. After a four-season stretch in which he posted an aggregate minus-43 defensive runs saved (DRS) in center field, Fowler suddenly ... was positive.

ESPN's Doug Glanville wrote about the turnaround at the beginning of last June. The explanation he extracted from Cubs manager Joe Maddon: Stats! Acting on the advice of Chicago's analytical team, Maddon convinced Fowler to play deeper. The result was fewer balls hit over his head, which invariably go for extra bases.

At the time, Fowler's DRS was plus-1, per Baseball Info Solutions. That's exactly where Fowler ended the season, resulting in a 12-run improvement over his average between 2012 and 2015.

Combined with Jason Heyward's Gold Glove defense in right, Chicago's outfield defense became a key part of its off-the-charts run prevention.

The play-deeper scheme made sense on the very face of it: In 2015, Fowler saved 12 plays on shallow-hit fly balls, but 17 plays below average on deep balls. Last season, he broke even on the shallow and deep balls alike, with his 1 DRS on medium-depth balls. In 2015, the Cubs gave up a double or triple on 9 percent of balls allowed in play; last year that plummeted to 5.6 percent -- best in the majors. Suffice to say, it was a worthy trade-off.

It's an open question of what accounted for Fowler's improvement. Was it merely the change in positioning? Did he actually get better? Was it the impact of playing next to a superior fielder in Heyward? The answer to that question is important. But only to the Cubs insofar as it impacts Fowler's new team, the rival St. Louis Cardinals.

The Cardinals could certainly use a defensive boost. While their percentage of doubles and triples per balls allowed in play last season was near the league average, the team's overall outfield defense put up minus-3 DRS. The problem wasn't the primary center fielder, as Randal Grichuk was plus-7, and the Cardinals were plus-2 overall at that spot. The problem was left field, where St. Louis' minus-10 was 26th in baseball.

St. Louis' offseason solution was to sign Fowler to a five-year, $82.5 million deal to take over in center and bat leadoff. Matt Carpenter will drop to third in the order, and Grichuk will take over in left. Seems like a plan. However, for that plan to work, the Cardinals need Fowler to live up to his 2016 production in center, not revert to his 2012 to 2015 numbers.

Fowler was quizzed about his defensive improvement approximately 900 times last season, and his response was typically the rhetorical version of a shrug of the shoulders. In his mind, he was playing the same as always on defense but merely standing 15 feet farther back. If that boosted his metrics, fine. Who cares about metrics? As long as the team wins. Which it did. A lot.

There are many, many inherent difficulties in projecting what Fowler will do with the glove going forward. For one, he's in a new ballpark. Fowler's DRS in Busch Stadium since 2012 has been a collective plus-1, and it was plus-3 in the Cubs' nine games played in St. Louis in 2016. That's a good sign, but certainly nothing on which you'd want to base a projection.

The Cardinals have long been one of the most progressive organizations around, and if you really want to know how likely it is that Fowler retains his defensive uptick, you have to start with the most obvious data point of all: The Cardinals signed him. But we'd like to at least take a stab at going a little deeper, so let's burrow into our DRS database, look at one-year leaps similar to Fowler's, and apply some percentages to what occurred after that.

We're going to look at players who improved at least five runs from one season to the next and also have a subsequent season in which to compare. Of 5,678 player-seasons in the DRS database, only 488 (8.6 percent) made such a drastic improvement from one season to the next. So what about the season after that?

Bad news: Collectively, the group regressed by an average of 5.1 runs. Only 103 of them (21.1 percent) improved even more, while another 25 held steady. The rest (73.8 percent) declined. Of course, there's this: Because Fowler had such a horrific 2014 defensive season in Houston (minus-20 DRS), his 13-run improvement last season was his second straight leap. His minus-12 in 2015 in Chicago was no great shake, but it was a lot better than what he did in Houston.

Also, while all defenders as a group lost an average 5.1 runs after a big one-season jump, the regression wasn't nearly so steep for outfielders, which lost 2.2 runs per fielder. Among center fielders -- and at this juncture, the samples are getting pretty small -- that loss was just 0.7 runs.

There is one more factor to consider here: venue. Wrigley Field isn't necessarily a great place to play outfield. And neither is Colorado, where Fowler began compiling the old, bad metrics that dogged him until last season. Houston is pretty good, but that was only one season of Fowler's career. One way to measure this is to look at visiting team DRS, among outfielders, in each of the various ballparks since 2012:

If you want to toss out Fowler's Houston season as an outlier, the move from Wrigley to Busch should boost his quest to retain his defensive gains. Again, we can't emphasize enough that projecting defense is hard to do, and it takes a strong buy-in to DRS as a metric to believe any of this, but consider what we've determined:

  • Fowler's improvement was tied to something tangible (his positioning).
  • Fowler is going to an organization where his analytical uptick won't be ignored.
  • Fowler has improved significantly not only last year, but two years running.
  • His new home stadium is conducive to strong outfield play.
  • While Grichuk might not be Heyward in the outfield, Fowler should again be playing next to an above-average corner defender, and we haven't even mentioned that rocket-armed right fielder Stephen Piscotty's numbers are pretty good, too.
  • The bottom line is, while defensive metrics remain an area of uncertainty, there are more reasons to think that Fowler will retain his gains than not. If so, he'll upgrade the Cardinals' outfield defense.