Corey Seager is a budding star. A former North Carolina high school baseball standout, Seager was selected 18th overall by the Dodgers in 2012 and hasn’t looked back, tearing his way through six levels of the minor leagues before earning a September call up in 2015. The rookie with the calm demeanor performed very well during his late-season stint with the Major League club, starting over veteran shortstop Jimmy Rollins in the playoffs and convincing management in the process that he was ready to be the 2016 every day shortstop.
The 22-year-old wunderkind certainly lived up to the hype during his first full season in the Major Leagues. Seager stayed injury free, playing in 157 regular season games and finishing in the top-7 in wins above replacement (according to both the Baseball-Reference and Fangraphs versions of the statistic). What’s more, Seager played surprisingly good defense over a full season at shortstop. Standing at 6-4, Seager is one of — if not the — tallest shortstop since Cal Ripkin Jr., and the popular scouting narrative has been that his height would force a move to third base in the big leagues. (Third base requires less range and lateral quickness than shortstop and is thus easier to handle for taller players.) Perhaps the move will eventually happen, but it certainly wasn’t necessary in 2016 as Seager played above average shortstop defense according to prominent defensive metrics. The fact that he’ll be staying at shortstop for the foreseeable future is welcome news for the Dodgers; shortstop is a more important defensive position than third base, and Seager is thus more valuable as a shortstop than he is as a third baseman.
Unfortunately, MLB doesn’t publicly disclose player tracking data, so we’ll have to save an analysis of his defense for another post. Instead, let’s take a deep dive into the PITCHf/x data to see how pitchers tried — often unsuccessfully — to get Corey Seager out in 2016.
Consistent Corey Seager
Most rookie hitters experience extended slumps in their first season in the big leagues. Compared to the minor leagues, the majors feature not only the world’s best pitching but also improved scouting, more travel, a longer season, and more pressure, all of which can make for a harsh environment for newcomers. Knowing this, my initial thought with this exercise was to compare slumping Seager to non-slumping Seager in an effort to analyze how pitchers attacked him over time. But this turned out to be a fruitless endeavor, because Seager didn’t experience a prolonged slump during 2016. Check out Seager’s weighted on-base average (wOBA) by month last season:
One quick note regarding the usage of wOBA instead of mainstream statistics like batting average or slugging percentage. wOBA rewards hitters for the exact run values of distinct offensive events (singles, doubles, walks, etc.) by using run environment-specific linear weights. This is an improvement over other rate statistics like batting average — which weights all offensive events equally and does not reward walks — or slugging percentage — which arbitrarily weights different offensive events without regard for their actual run values. For example, slugging percentage weights a home run as three times more valuable than a single; in reality, this isn’t the case.
Back to the charts. The wOBA of the league-average hitter is typically around .320 (according to Fangraphs), and a fantastic wOBA is above .400, so Seager was consistently excellent against right handed pitchers and league-average against left handed pitchers. The small month-to-month variation is to be expected, especially with small sample sizes. Remember, any given month is a random sample — with arbitrary end points — of Seager’s true (i.e., mean) talent level. The sample is therefore subject to the same type of random variation around the mean associated with typical sampling of a distribution. The fact that we don’t see a precipitous drop means it’s safe to conclude that he was consistent on the whole, especially for a rookie getting his first taste of starting in the big leagues. This speaks not only to his talent but also to his makeup and willingness to make adjustments, two qualities which bode extremely well for his long-term development.
What types of pitches did Seager see?
So, Corey Seager didn’t exactly slump in 2016. But let’s still examine pitcher strategy, even though the strategy was not successful for prolonged periods of time.
First, let’s investigate the types of pitches Seager saw. The below depicts the percentage of each pitch type faced by Seager in 2016 (by month and pitcher handedness).
You’ll notice (1) that Seager saw about half as many pitches from lefties as he did from righties and (2) that the Seager pitch mix shifted throughout the year. Seager saw more curveballs and fewer sliders from lefties as the year wore on, and he saw fewer fastballs and more changeups from righties towards the end of the season.
With a bit of league-wide context, these charts are convincing evidence that pitchers attacked Seager differently than they pitched the average hitter. Using the graph on the left, Seager saw a breaking ball (i.e., slider or curveball) from lefties about 35% of the time. Of the hitters that saw at least 100 pitches from lefties this season, the league-wide average breaking ball rate was 24% (with a standard deviation of roughly 9%), showing that Seager saw a significantly higher percentage of breaking balls than the rest of the league.
Similarly, the right graph shows that Seager saw a changeup roughly 20% of the time from righties. (The actual figure is 18%.) The league-wide average changeup percentage (among hitters who saw over 100 pitches from righties) was 9% with a standard deviation of 4.4%. This means that Seager saw changeups at a 2+ standard deviation higher rate than the rest of the league. Indeed, Seager faced the second highest number and fifth highest percentage of changeups across the entire Major Leagues last season.
Where were those pitches located?
We’ve seen from the above that lefties attacked Seager primarily with a combination of fastball-breaking ball, and righties attacked Seager primarily using a combination of fastball-changeup. In an effort to complete the picture, let’s take a look at the last piece of the puzzle: where those pitches were located.
To do this, I created a strike zone heat map by grouping each of Seager’s roughly 2,700 pitches seen into equally sized buckets. The heat map shows the relative location of all pitches which satisfy a given combination of outcome, month, pitch type, pitcher handedness, and count. The heat map is drawn from the perspective of the catcher, and the coordinates of the top and bottom of the strike zone are specific to Seager.
A static shot of the heat map is pasted below, but please go play around with the tool on Tableau Public! (Unfortunately, WordPress would not let the workbook be directly embedded in this post.)
Using the heat map, we can see that left handed pitchers attacked Seager with breaking balls away and fastballs middle-away; they had the most success when their fastball was elevated in the zone and when the breaking balls were thrown down and away (especially when Seager was behind in the count). As for righties, the heat map shows us that pitchers had success when they threw changeups down and away and breaking balls down and in. Finally, and not surprisingly, Seager had success against both righties and lefties when pitches were thrown in the middle-inside part of the strike zone.
Put it all together, and we have a bit of a lens into how pitchers approached Corey Seager in 2016 and what we might expect in 2017. Seager saw a below average percentage of fastballs from both lefties and righties; lefties attacked Seager instead with a heavy dosage of breaking balls, and righties attacked Seager with a league-leading number of changeups.
We can expect more of the same next season. Seager has proven that he can hit the best fastballs in the world, especially those in the middle-third of the plate, so he should expect to continue to see a heavy dosage of off-speed pitches away — in all counts. Changeups like this nasty one from Kyle Hendricks are something that Seager will have to continue to deal with moving forward.
But the smart money is on him to figure it out. He is an extremely balanced hitter who is rarely fooled, and he possesses a veteran-like demeanor that will serve him extremely well moving forward as pitchers adjust their game plan.
Best of all from the Dodgers’ perspective? He isn’t arbitration eligible until 2019, and he’s under team control until 2022 when he finally becomes a free agent. Based on his 2016 performance, it sure looks like the Dodgers have found their shortstop of the future.