Corey Seager’s Powerful Weekend

Last year’s brilliant rookie class was exciting for many reasons, one of which was that it brought the arrival of an infusion of talent to the shortstop position in Carlos Correa, Francisco Lindor, and Addison Russell. Remarkably, we were assured that even more young shortstops are on the way – an assurance reinforced by Corey Seager’s strong debut last September and his near unanimous presence atop top-100 prospect lists this past winter. But, at the start of the season, it was less-heralded rookie shortstops Aledmys Diaz and Trevor Story catching all the headlines. Where was Corey Seager?

While Story spent the month of April hitting 10 home runs and Diaz spent it batting .423, Seager posted an unremarkable 92 wRC+ through 106 plate appearances. He put up decent enough plate-discipline numbers — a 8.5% walk rate and 14.2 strikeout rate — but a low BABIP (.275) and low ISO (.146) kept him from producing at the level expected of the sport’s top prospect, whether those expectations were fair or not.

Ever since the end of April, however, Seager has been quietly reestablishing his place among the league’s best players. Well, he was going about it quietly, until this weekend. On the off chance anyone had forgotten about Seager or prematurely written him off as over-hyped, he reminded the baseball world Friday night that he’s exceedingly worthy of our time and attention when he did this to Braves pitcher Julio Teheran:

Then this:

And then, for good measure, he did this to Braves reliever Hunter Cervenka:

Barely a month past his 22nd birthday, Seager became the youngest player to hit three homers in a game since a 21-year-old Boog Powell accomplished the feat in 1963 and the sixth-youngest overall since 1913. Vin Scully announced the following night that Seager was the first rookie shortstop in major-league history with a three-home-run game. Unfortunately for the Braves, Seager wasn’t done. He followed up his Friday night offensive outburst with an equally impressive 3-for-5 game on Sunday during which he homered twice more.

However, as I mentioned above, this weekend didn’t mark Seager’s sudden return to relevance. As the shine has begun to wear off the impressive debuts by Diaz and Story, Seager has been steadily climbing back up towards the level of production expected of him. On the strength of this weekend, he’s now essentially caught up to the OPS of his fellow rookie shortstops:

Given the expectations heading into the season, it’s no surprise that Seager has begun to turn it around offensively. His defensive production, on the other hand, has been somewhat unexpected. As a prospect, it was often posited that Seager would have to slide to third base sooner or later due to a lack of speed necessary to hold down the shortstop position.

Despite his reputation, defensive metrics place Seager among the top fielding shortstops in the game so far this year. If you’ll forgive an obligatory small-sample-size warning, defensive metrics must be viewed with a healthy degree of skepticism just two months into the season. I wanted to bring it up, though, because that defensive value has contributed to Seager’s WAR soaring beyond his shortstop compatriots. In fact, Seager has currently produced more wins than any other rookie, regardless of position — and by a wide margin, too:

Not only is Seager establishing himself among the top of the rookie class, he ranks third in WAR among all major-league shortstops, trailing only Manny Machado (3.3 WAR) and Xander Bogaerts (3.0). So, how has Seager gone about leaving his April mediocrity behind to become one of the league’s best shortstops? There have been two key changes in his production at the plate and they’re very much related to each other.

First, he’s seen a marked improvement in his ground-ball rate. At the start of the season, Seager struggled to keep the baseball off the ground. It didn’t matter where the pitch was located, because he was rolling over everything. Compare his April GB/P strike-zone heat map (left) to his heat map since May 1st (right).

The ground-ball rate has declined sharply, particularly up in the zone. The fact that he’s no longer driving pitches into the ground brings us to the biggest change for Seager, no matter how obvious it may be: he’s hitting for power. Here’s another side-by-side heat map comparison, but this time it’s of his ISO against pitches:

Once again, his April map is on the left and the heat map on the right shows his ISO since May 1st. The difference between the two is night and day. Back in April, Seager was still turning on pitches down the middle, but demonstrating little power anywhere else in the zone. Now, Seager is pummeling balls all over the zone and the pitches up in the zone that he had been hitting on the ground are getting hit for power.

It sounds overly simplistic to chalk up a guy turning his season around to power, but that’s really all there is to it. Since April, his walk rate has actually declined and his strikeout rate has risen. His BABIP has improved, but only slightly and that can likely be attributed to the same improved quality of contact that’s resulting his power surge.

Ultimately, the power he displayed at Dodger Stadium this past weekend is a perfect illustration of what’s gone right for Corey Seager recently. It’s that impressive power from an up-the-middle position that made Seager such a special prospect heading into the season and tapping into it now has helped him separate himself from the other rookies in the league in his quest to become one of the best shortstops in the game.