The Nationals made an enormous Winter Meetings splash by acquiring Adam Eaton from the White Sox for highly-regarded pitching prospects Lucas Giolito, Reynaldo López, and 2016 first-round pick Dane Dunning, and the ripple effects Wednesday's deal will have in Washington will be huge. Eaton is likely to take over center field, pushing Trea Turner back to shortstop, and turning incumbent shortstop Danny Espinosa into a reserve or a possible trade option.
There's little doubt that the offense will be far better off for this change, because Eaton (.284/.362/.428, 115 wRC+) is a huge improvement on both non-Turner outfielders Michael Taylor (.231/.278/.376, 72 wRC+) and Ben Revere (.217/.260/.300, 47 wRC+, non-tendered after the season) as well as Espinosa (.209/.306/.378, 79 wRC+), the three hitters who you'll see far less of next season. So in that sense, it's a win.
But what about on defense? Following the trade, manager Dusty Baker and general manager Mike Rizzo were asked how this all makes the team better defensively. Rizzo, perhaps notably, chose not to answer. Baker said that "it's a possibility that we could have Golden Gloves everywhere." So what does this all do to Washington's fielding? Let's find out.

Center field: More Eaton, less Turner
Eaton's defensive value has been notoriously difficult to pin down, because he's switched positions, played through a shoulder injury, and basically had wildly differing yearly scores per the advanced defensive metrics. Looking at Defensive Runs Saved, Eaton was +11 in center field in 2014, -14 in center field in 2015 and +22 in right field in 2016. Given all that, it's tough to know what to really expect from him back in center in 2017, because single-year defensive metrics aren't always reliable even when they aren't fluctuating like this.
Rizzo pointed out that it was "one of the few times the analytical information matched up with scouting eye," so perhaps that helps somewhat, given that 2015 was the season Eaton was dealing with injury and that "he comes from a high WAR as a corner outfielder, so we feel he's going to be a solid performer in center field."
One part of Eaton's fantastic 2016 that probably won't be affected by a position switch would be his arm, which showed a 94.5 mph average on "competitive throws," the 10th-best average of the 166 outfielders with at least 15 qualified throws. By FanGraphs' throwing arm metric, his 2016 was the second-most valuable year on record, which dates back to 2008.
The 2016 Nats weren't bad in center, though, ranking two runs below average in DRS and three runs below in UZR. For his career, Eaton has rated as a slightly below-average center fielder, at -8 runs by both DRS and UZR. In an extremely small sample, Turner -- who mixed breathtaking speed with sometimes questionable route-running, not unexpected due to his inexperience -- rated as a slightly below-average center fielder. While admitting this comes with uncertainty, the effect here seems to be limited in either direction.
What's worth noting as well is that Eaton had the third-most balls hit to him of any outfielder in the Majors this year, and defense is an opportunity-based pursuit. (You can't look good without batted balls coming your way.) That's not likely to repeat itself again, so fewer opportunities in a position where he'll be stretched more probably pull down Eaton's defensive value, leaving us in the same place -- last year's elite right fielder sounds like next year's around-average center fielder.
Rizzo also added that "in the short term, he will play center field," which perhaps adds more context than he intended. Jayson Werth has only a single year left on the seven-year deal he signed following the 2010 season, making it easy to imagine that Eaton and Bryce Harper are the team's corner outfielders in 2018 -- with another center-field hunt ensuing next offseason.

Shortstop: More Turner, less Espinosa 
Without question, getting Espinosa's bat out of the lineup is a big win for Washington. But what does losing his glove mean? Espinosa had baseball's strongest shortstop throwing arm, and his +8 DRS indicates that he was an above-average fielder. Turner got into just six innings at the position in 2016 for the Nationals, so we don't have much to judge him on there.
So let's go to the scouting reports, based on what was seen of Turner playing the position in the minors. "He won't be a Gold Glover but he can be a steady defender," said MLBPipeline.com's 2015 report. "He's a steady if unspectacular defender," agreed the MLBPipeline Prospect Watch top shortstop list in January. "He has enough glove to be a decent shortstop or an above-average second baseman," concurred FanGraphs before the season.
That's a lot of agreement, isn't it? None of that's saying that Turner can't handle the position, but it does seem like he may not be quite the improvement on Espinosa with the glove that he'll obviously be with the bat. And if that's true, the ultimate outcome of "maybe the same in center" and "perhaps a slight downgrade at short" isn't necessarily the big step up it seems -- though, again, the boost the lineup gets might more than cancel that out.
Ultimately, Rizzo may have hit the nail on the head when talking about the versatility of his roster.
"It leaves us with a lot of options," said the GM. "Positional flexibility is a good thing to have, we have it, we have several players that can play different positions successfully. Trea has proven he can play shortstop, center field, second base effectively. Bryce has proved he can play center field, left and right. Same thing with Eaton. So we have a lot of flexibility and it allows us a lot of ways to put a lineup on the field."
Rizzo didn't even mention the likely possibility that Ryan Zimmerman gets injured (or benched, given his poor 2016), which could push Daniel Murphy to first and Turner to second. Likely, we're going to see a lot of different combinations in 2017, and while the price was quite high, Eaton has been a borderline star.
The Nats may not actually have a better defense. They are, however, a better team.