Red Sox: Examining Rafael Devers’ sophomore slump

BOSTON, MA - OCTOBER 08: Rafael Devers
BOSTON, MA - OCTOBER 08: Rafael Devers /

Rafael Devers has struggled in his second taste of the big leagues. But has his performance dropped or could this slump be mostly smoke and mirrors?

The date was August 13, 2017. The Boston Red Sox had dug themselves into a 2-1 hole against their arch rival in the Bronx and, as Aroldis Chapman walked out from the bullpen, hope seemed to vanish. Hanley Ramirez was the first to face the flamethrower and Chapman threw three straight triple-digit fastballs right by the former MVP. The ever imposing 6’4 Cuban fireballer looked as good as ever.

Stepping to the plate next was a stocky 20-year-old by the name of Rafael Devers. Devers had been scorching hot in his first couple of weeks in the majors; to date, he had slashed .327/.393/545 over 61 plate appearances, but as he stood in against one of the league’s most dominant closers many fans prepared themselves for a “welcome to the big leagues” type of moment.

It’s a situation we’ve all seen many times. The new flash in the pan rookie steps up to face one of the game’s elites and is made to look foolish. That’s why when Chapman reared back for 102.8 mph fastball in a two-strike count nobody expected Devers to come close to it. That is until the ball landed in the left-field bullpen.

That was the kind of rookie season Devers had in 2017. Despite being the youngest player in the lineup, Devers’ 111 wRC+ was the highest mark on the team among players that came to bat at least 200 times. He hit .284/.338/.482 with 10 homers in 58 games and looked as much as anyone in the league like a budding superstar.

2018 has not been as kind to the young third baseman. His success last season has not translated to a strong showing this year. Through his first 59 games this season, Devers has hit just .228/.283/.402; good for a wRC+ of 77.

Devers is only 21 years old and thus some growing pains this season are not surprising or even too concerning. Still, when your bat-first third baseman is hitting 23% below league average it’s worth asking what has changed since last year?

Those who watch a lot of baseball know that usually when a sophomore struggles in the big leagues the reason is that pitchers have made adjustments. Either they’ve found a hole in the newbie’s swing or just realized he can’t lay off pitches in the dirt. So let’s look here first to see what’s going on with Devers.

Above is the percentage of pitches Devers is seeing by location in both years. As you can see, the charts are nearly identical. They’ve pitched a little bit more down and in, but, considering that the difference in those percentages is a handful of pitches, you’d really have to be grasping at straws to see that as a red flag.

Further, Devers isn’t really getting iced in that part of the zone anyway. There doesn’t appear to be some obvious hole pitchers are exploiting more than last season. They aren’t really mixing their pitches differently either.

201751.5% (93.5)16.4% (83.9)5.8% (89.8)9.3% (79.6)14.2% (84.8)2.8% (84.5)1.00%
201849.5% (92.9)16.6% (83.8)4.5% (88.4)7.5% (78.2)18.5% (83.7)3.4% (85.5)1.30%

The above table is the percentage of offerings by type with average velocity in brackets. If these abbreviations don’t look familiar, Fangraphs provides a useful cheat sheet. The takeaway here is that besides a slight uptick in changeups, the spread of pitches Devers has seen, both by location and type, is essentially the same.

So if pitchers aren’t approaching Devers differently then the next logical thing to check would be Devers’ approach. Has Devers been missing pitches that he hit last season?

Well, he seems to be missing a little more often up in the zone but, as we can see on the first graphic, he’s seen very few pitches on that part of the plate both years anyway. Overall his contact profile doesn’t appear any more concerning than it did last season. So what about his plate discipline?

Devers walk rate has remained almost identical (7.5% in 2017 and 7.4% in 2018) but his strikeout rate has seen a slight uptick from 23.8% to 26.6%. That’s not entirely insignificant, but it’s also not a huge deal. Both of those numbers are fairly high but within the range of normal for sluggers. In fact, J.D. Martinez struck out 26.2% of the time last season while managing to be the best hitter on the planet.

The strikeout uptick would be more concerning if it meant Devers was chasing more pitches out of the zone. However, Devers’ swing percentage on pitches off the plate has actually dropped from 38.5% last year to 37.3% this season.

So while there are some warning flags here, Devers’ approach does not seem to be the main problem. He’s always been a bit of a free-swinger and probably always will be, but his profile is in line with last year. And thus the last logical place to look for an explanation is Devers’ batted ball profile. Here’s where things get interesting.

Devers has seen his BABIP drop from .342 in 2017 to .276  in 2018. That’s the kind of drop that might cause a player’s batting average to drop 56 points. But hitters have fairly limited control of their BABIPs.

If a BABIP were to drop that far based on a change in batted balls, we would expect to see a drop in hard contact or a large change in the spread of batted ball types or locations. So let’s take a look.

201715.3 %49.1 %35.6 %13.8 %34.5 %33.9 %31.5 %18.2 %47.3 %34.5 %
201814.4 %45.6 %40.0 %10.9 %38.5 %36.6 %24.8 %19.3 %44.1 %36.6 %

As you can see, Devers has lifted the ball a little bit more, but not enough for this large of a BABIP gap; especially considering he’s increasing fly balls by selling out grounders and, while groundballs have a higher average BABIP, the gap between the two narrows for very slow players. The quality of his contact remained about the same and in fact, according to Statcast, his exit velocity on the season has increased and his percentage of barrels has remained about the same. (there’s no easy way to isolate Devers on that site but you can switch between seasons and search for him).

The fact that the quality of his contact has not dropped has led to a large gap between Devers’ expected results per Statcast and his actual results. Statcast has his expected batting average and slugging percentage in 2018 at .241 and .430 respectively. They also have his expected wOBA at .315, which is much prettier than his actual wOBA of .286.

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So those expected stats make it seem like Devers has only been a little worse than last year instead of a lot worse. But hold on; we still have to see where Devers would have been expected to perform last year based on his quality of contact. Statcast has his 2017 expected batting average and slugging percentage at .229 and .416 respectively and his expected wOBA at .301. Those numbers are far below his expected lines from 2018.

This means that Devers was both very lucky last season and very unlucky this season. He actually should have better results this year than in 2017 with neutral luck, but instead, his numbers have plummeted.

There’s one more interesting note in his batted ball data that may help to understand this change. If you look again at the table above you’ll see that Devers 6.7% less of the time. It turns out that in 2017 Devers had a startling .519 batting average and .942 slugging percentage on balls hit to the left side. In contrast, this season Devers average and slugging percentage on balls hit to the left side are .256 and .538 respectively. His batting average on balls to left field and center field is actually higher this season, so one begins to wonder what’s going on. The breakdown of the quality of his contact to left field is telling.

2017As L to Left15.7 %27.5 %56.9 %20.7 %13.8 %17.3 %46.2 %36.5 %
2018As L to Left15.0 %22.5 %62.5 %12.0 %12.0 %15.0 %65.0 %20.0 %

The spread of Devers’ batted ball types may have actually improved. He’s turned infield pop-ups into fly balls. That’s good. But he’s also hit the ball hard 16.5% less often. That contact has fallen into the medium hard hit range instead and perhaps in Fenway that’s frequently the difference between the ball finding a left fielder’s glove and scraping the Green Monster. Fangraphs’ spray charts have limitations; namely, I can’t adjust by ballpark and it isn’t 3D so we can’t see if these balls hit the wall. However, if you check out his spray charts from the two years, it does seem like there are a lot of balls to left field in 2017 that could have hit the wall in Fenway that aren’t there this season.

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So Devers’ steep drop-off this season isn’t as steep as it appears at first glance. The quality of his contact overall suggests he actually improved this season and pitchers have done little to change their approach. It seems the only red flag is that Devers is using left field less effectively than he did last season. It’s hard to say what has caused him to hit the ball to left with less authority, but in this small of a sample, I doubt the reason is earth-shattering. He’s still 21 and has all the talent in the world. Expect this kid to bounce back soon.