Naturally, the addition of Kyle Schwarber by the Washington Nationals sparked concerns about the slugging outfielder’s defense. But perhaps more questions should key on what Victor Robles did in center field last season and what he has to do moving forward.

Unless there’s a designated hitter in the National League this year, Schwarber will play left field for the Nationals. They signed him to a one-year, $10 million deal Saturday — with a $7 million base salary and a $3 million buyout if a mutual option is not picked up. They did so to beef up a lineup that already included Juan Soto, Trea Turner and Josh Bell. And almost immediately, the deal was publicly defined by Schwarber’s defense.

“No one likes me in left field, for some reason,” Schwarber said during a video conference call with reporters Saturday. “Everyone likes to look at these numbers and stuff and just bang me on it.”

Schwarber smiled like someone who’s too accustomed to hearing about his flaws. A breakdown of his defense — and Robles’s, too — should come with a few disclaimers: Fielding analytics are inexact. Those provided by FanGraphs and MLB’s Statcast are used in front offices but are best employed to spot outliers and anomalies. And 2020, a 60-game season amid the coronavirus pandemic, was a statistical anomaly all its own.

But Schwarber was right to say he has his critics as a left fielder. One obvious exception, of course, is a Nationals team that’ll put him there and hope his offense tilts back toward his 38 home runs and .871 on-base-plus-slugging percentage from 2019. They seemed to make a similar calculation in trading for Bell, who’s a bad defensive first baseman but valuable for his bat. Each are delicate trade-offs for a club built around its rotation.

The Nationals, like all teams, evaluate defense by looking at scouting reports, internal data and numbers that are available to fans. And then they have their own way of weighing offensive pluses against defensive minuses.

Defensive runs saved, a catchall FanGraphs metric that measures players in relation to the average, ranks Schwarber as baseball’s second-worst left fielder since 2017. Outs above average, a range-based Statcast metric, is similarly unkind to Schwarber, given his lack of speed and inability to spring into the gap.

He fares better in some advanced categories, such as Ultimate Zone Rating, because his arm strength is factored in there. Yet, as he acknowledged, the numbers consider Schwarber a definitively poor defender. He just doesn’t feel that’s fair.

“I view myself as a good outfielder,” Schwarber, 27, said Saturday. “I’m going to go out there, [and] I’m going to make the play that I need to make.”

Let’s assume that’s true. Let’s assume that, in 2021, Schwarber makes most of the plays within the bounds of his skill and athleticism. Let’s even assume he improves under Manager Dave Martinez, a former outfielder and Schwarber’s old bench coach with the Chicago Cubs. There’s a very good chance he’s still statistically subpar.

And there is where Robles comes in.

Two seasons ago, Robles was arguably baseball’s best defensive outfielder. He led all qualified outfielders with 25 defensive runs saved. He was first in outs above average with 23. He was surrounded by slower-footed defenders — Soto in left, Adam Eaton in right — yet the Nationals’ outfield ranked in the top half in most advanced fielding stats. That was Robles’s doing.

Then he slipped in 2020 and the defense did, too. Robles added around 15 pounds of muscle, according to Martinez, and struggled to adjust at the plate and in the field. He ranked 48th among qualified outfielders with minus-4 defensive runs saved. He slipped below average in UZR and finished with two outs above average, only marginally more than Soto, Eaton and, yes, Schwarber.

The Nationals’ outfield, in turn, cratered to 29th out of 30 teams with minus-43 defensive runs saved. The team’s overall defense ranked dead last. In the truncated year, Soto’s and Eaton’s defense was worse but didn’t fluctuate a ton from prior seasons. So just like in 2019, Robles was the difference.

“We’ve got to remember he’s such a young kid still, and he’s still got a lot to learn,” Martinez said of Robles in September, before the 23-year-old headed to play winter ball in his native Dominican Republic. “I still believe that, one, he’s going to be a Gold Glover. And two, this kid is going to put up some numbers as a hitter. We’ve just got to keep working with him.”

It would go a long way if Robles could realize that Gold Glove prediction. At the very least, it would help a whole lot if he could get back in the neighborhood. Last summer, he still made his share of eye-popping plays. He scaled the wall to rob a home run in Atlanta. He made a 288-foot throw from deep center, on the fly to first base, to complete a double play. The hints of his defensive greatness were there.

Too often, though, was the scene of Robles charging in for a shallow pop-up, a few steps late, and watching it land somewhere close to him, Soto and Turner at shortstop. Routine became difficult in 2020. It appeared worse in contrast to 2019, when Robles’s glove, arm and speed helped lift — and sometimes hide — the outfielders to his left and right.

There is evidence he can do that. Signing Schwarber may mean the Nationals see it happening again.