Each week on the Statcast™ Podcast, hosts Mike Petriello and Matt Meyers dig into the world of Statcast™ and advanced metrics, exploring the most important topics in baseball through the lens of the groundbreaking Statcast™ technology. Download, subscribe and help others find the show by leaving a rating and review on iTunes or your favorite platform.
It's still early in the season, but it's also not too early, because this season began back in late March. Some teams have already played 30 games, or nearly 20 percent of their schedule. What we've seen so far may not absolutely predict what will happen, but we can at least look at what has happened and see if there's anything to take away from it.
For example: Which outfield defenses have taken the biggest steps forward this year? Can we find differences already? Fielding metrics are tough in small samples, but it's worth a look to see what the first month has brought us.

We'll use Statcast™ data to see what we can see, but because we're trying to compare a partial season to a full season, we can't really use Outs Above Average, our range-based metric, here. Instead, we'll do something different; we'll look at it on a rate basis.
The way we do that is to look at the difficulty of batted balls hit to fielders (and teams), which allows us to say how many opportunities that fielder (or team) would be expected to catch and how many they made. The difference between those numbers tells you how much value added (or not) occurred.
For example, Byron Buxton was expected to catch 87 percent of balls hit to him last year, and he caught 94, giving him an excellent +7 points added. Matt Kemp was expected to catch 86 percent and caught only 76 percent, a 10-point gap.
You can see last year's team numbers here, and 2018's team numbers here. These are 2018's outfields with the most improved defensive range so far.
1. D-backs (5 point improvement in performance from 2017)
This is going to be a recurring theme in these rankings: The D-backs have improved their outfield defense in large part because they have different (better and healthier) outfielders than they had last year. Sometimes, it is that simple.
In 2017, Arizona spent the first half of the year with Yasmany Tomas (who should be a designated hitter), Daniel Descalso (who is an infielder) and Chris Herrmann (who is mainly a catcher) in left field. Center fielder A.J. Pollock missed more than a month with a groin strain, and when he returned, he'd soon find that next to him in right field was J.D. Martinez, who is far better known for his massive bat than his unremarkable glove. It wasn't a strong group, reflected in the D-backs' minus-6 OAA, tied for 17th in the Majors.
This year, it's different. Tomas is in Triple-A. Hermann is in Seattle, Martinez is a designated hitter in Boston and Descalso is back where he belongs in the infield. Pollock is healthy, David Peralta has manned left field and right field is being shared by newcomer Jarrod Dyson (long known for his elite defense) and the versatile Chris Owings.
All four Arizona outfielders rate as above-average so far, led, somewhat shockingly, by Owings, who is more of a utility man than an outfielder. He's been expected to catch 80 percent of balls hit his way, and he's actually come down with 90 percent, most notably making this extremely impressive grab last month:

(Owings and Pollock each sat out the next day, but were otherwise unhurt.)
Dyson, meanwhile, has made a career out of elite defense, and he has been a valuable addition to the National League West-leading D-backs.

Remember, also, that this isn't even Arizona's outfield at full strength. The D-backs traded for Steven Souza Jr., himself a strong defender, expecting he'd be their starting right fielder. But Souza injured his shoulder in Spring Training, and he hasn't yet made his Arizona debut, though he's expected back soon. When he is, Dyson and Owings will provide outfield depth off the bench.
In addition: It's interesting to wonder if the expectation that Chase Field's new humidor would lead to more balls in play helped push the acquisitions of Dyson and Souza.
2. Pirates (4 point improvement in performance from 2017)
For years, we looked at the trio of Andrew McCutchen, Starling Marte and Gregory Polanco as one of baseball's best outfields, but it fell apart in 2017, as Marte was suspended, Polanco was injured and McCutchen's final season in Pittsburgh wasn't a strong defensive campaign. The Pirates' outfield ranked 27th in Outs Above Average in 2017.
Flash forward to this year … and Pittsburgh's outfield has been arguably baseball's best. It helps a little to have McCutchen in San Francisco, but this really isn't about him. It's about the fact that Marte and new addition Corey Dickerson have been, so far, two of the best defensive outfielders in the game.
Maybe that's not surprising about Marte, because he's long had a reputation for being a strong defender. However, last year, in his truncated season, he was only about average (88 percent expected catches, 88 percent actual catches). This year, Marte has been getting opportunities that are slightly harder (85 percent expected catches), and he's making more of them (90 percent actual catches made).

But really, the story here is about Dickerson, who spent a good portion of 2017 as Tampa Bay's designated hitter and has never been regarded as a strong defender. In addition to getting off to a hot hitting start -- .311/.354/.534 through his first 27 games -- he's been perhaps baseball's most improved fielder.

Even as recently as Tuesday night, Dickerson was out there making nice-looking catches. Let's not misconstrue a single month of good defensive play to suggest that after years of inconsistent work, Dickerson is now some kind of elite outfielder. But let's also point out that based on the limited sample we've seen so far in 2018, he's done everything expected of him, and then some.

3. (tie) Brewers (3 point improvement in performance from 2017)
Well, this one's easy -- or at least you'd think it would be. Milwaukee traded for Christian Yelich, who is a very good fielder. It signed Lorenzo Cain, who is a very good fielder. The Brewers haven't played first baseman Eric Thames out there in 2018, and Ryan Braun isn't getting as much time, because he's playing more first base now. They have better players now.
As you'd imagine, Cain rates well (85 percent expected catches, 87 percent actual catches), because he was our fourth-best outfield defender last season.

Yelich has been good, too. But the surprising thing here is that Domingo Santana, never considered a strong defender, is off to a good start. In each of the previous two years, he contributed negative defensive value, underperforming by five points in 2016 (81 percent expected, 76 percent actual) and two points in '17 (87 percent expected, 85 percent actual). So far in 2018, Santana has been four points better than average (93 percent expected, 97 percent actual). He's hauled in almost everything that's come his way.

So why is Milwaukee's placement here still somewhat surprising? Because despite the influx of talent in Cain and Yelich, and the early improvement of Santana, the Brewers are without their best defender from 2017. Keon Broxton lost his job after hitting only .220/.299/.420 last year, but he was also a near-elite defender. The fact that Milwaukee could still get better even without him tells you a lot about how well this group is playing.
3. (tie) Dodgers (3 point improvement in performance from 2017)
Maybe it's surprising to see the Dodgers here, but then again, they weren't rated very well in 2017, finishing just 24th overall in outfield OAA. A lot of that makes sense, actually, because neither Curtis Granderson (who underperformed average by two points) nor Joc Pederson (who underperformed by five points) were strong, and Chris Taylor, who was average, was playing his first year as a full-time outfielder.
Pederson noted that improving his conditioning was a priority this offseason, and he's been slightly better, but the real story here, in addition to the usual contributions of Yasiel Puig, is that Taylor has been much improved -- and that Matt Kemp has shockingly been valuable.
Taylor, remember, was primarily a shortstop in the Minors. Prior to 2017, he started 79 Major League games, and every one came in the infield. Pressed into duty as a center fielder in '17, Taylor was basically average (89 percent expected, 89 percent actual), which is something of an achievement in itself. So far in 2018, he's been far better than that, adding real value (90 percent expected, 94 percent actual).

Kemp, meanwhile, was near the bottom of the list of all outfielders in 2017, underperforming by 10 points. This year, in apparently better shape that's led to noticeably improved running speed, he's been enormously better. Kemp has been expected to make 94 percent of the opportunities he's seen, and he's made 96 percent.
The Dodgers have seen valuable work from utility man Enrique Hernandez as well, as he's received only a few chances, but made the most of them, adding three points of value.

On the other end of the list, the Mariners, Orioles and Rays have taken the biggest steps back, and little of that is surprising. Seattle lost Dyson, added Ichiro Suzuki and has been working to transition Dee Gordon to a new position in center. Tampa Bay, meanwhile, has been without the elite Kevin Kiermaier for weeks, thanks to a thumb injury.