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Which Max Kepler is the real Max Kepler?

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The one who can hit left-handed pitching or the one who can’t?

MLB: ALDS-Minnesota Twins at New York Yankees Brad Penner-USA TODAY Sports

This past offseason the baseball leadership of the Twins organization looked prescient, having signed right fielder Max Kepler to an early career contract extension before the 2019 season. The $35-million guaranteed contract covered the 2019 through 2023 seasons and looked like a shrewd bargain for the organization after Kepler’s breakout 4.4-fWAR/4.1-bWAR 2019 campaign. That breakout 2019 season saw him slash .252 / .336 / .519 and bash 36 homers, 32 doubles, and score 98 runs, resulting in the first above average offensive season of his big league career (121 wRC+). Heading into the delayed 2020 season, expectations were high for Kepler and many believed he’d established a new performance baseline. A generally accepted rule of thumb for valuing players is that 1 win above replacement costs about $8-million on the free agent market. By that crude measure the Minnesota organization essentially broke-even on the cost of Kepler’s extension in the first full campaign it covered. Given his age, unconventional baseball background, and strong minor league performances, there was optimism that he would develop even further, positioning the organization to profit handsomely for years to come.

Unfortunately, like a lot of things in 2020, Kepler’s season did not go according to plan. In 48 games, Kepler slashed .228 / .321 / .439 with 9 homers, 9 doubles, and 27 runs scored. If Kepler had played 130 games (roughly the same proportion as the 48 he played out of 60) those counting stats project to about 24 homers, 24 doubles, and 73 runs scored. He was again above average offensively overall (107 wRC+) but below the high expectations placed upon him heading into the season. In the end, his 2020 more closely resembled his pre-extension 2018 campaign (.224 / .319 / .408; 98 wRC+) than his 2019 breakout.

Which version is the real Max Kepler? The 2019 star version? Or the 2020 (and 2018) average-ish version? What factors drove his breakout and subsequent return to earth?

Career Context

Kepler broke into the majors for good in the 2016 season. In the five seasons since, he’s been remarkably consistent from a rate stat (batting average, on-base percentage, slugging percentage) point of view:

His batting averages have ranged between .224 and .252, and his on base percentages between .309 and .336 in all five seasons. The only notable outlier on the chart above is the .519 slugging percentage in 2019. Otherwise, he’s slugged between .408 and .439 in the other four seasons. Kepler’s triple-slash stats have been roughly Major League average over that time span. He’s been slightly below average in batting average and at or above average in on-base percentage and slugging percentage. The annual Major League averages for those three stats in the same time period have been as follows:

The comparison is a little less rosy when we focus just on right fielders, Kepler’s primary position. Of Kepler’s 543 career starts, 435 of them have come in right field. It is a position that commands a higher level of offensive production and that expectation is reflected in the stats produced by right fielders the past five seasons:

Compared to the MLB-wide, all-position data showed above, right fielders’ numbers are a few points higher across all three categories, and especially in slugging. It’s clear the stereotype of the slugging corner outfielder exists for a reason.

Kepler is one of 51 right fielders who have logged at least 1,000 plate appearances in the past 5 seasons. Among them, he ranks 46th in batting average (.238), 40th in on-base percentage (.320), and 27th in slugging percentage (.445). By wRC+ (102), he ranks 33rd. Despite those slightly below average offensive stats Kepler rates 10th out of the 51 in total wins above replacement (10.8 fWAR), a testament to his strong defensive abilities and the Twins’ commitment to giving him consistent playing time.

Against Left-Handed Pitching

Like many young, left-handed batters, the key to unlocking Kepler’s full potential rests on the ability to consistently hit left-handed pitching. The Twins, to their credit, have given Kepler substantial opportunities against left-handers in his young career. Instead of shielding Kepler from lefties and maximizing short term interests, the team has largely let him play, regardless of the pitcher on the mound. These decisions were both in the best interest of his development and the long term outlook of the franchise.

In 654 career PAs versus left-handed pitching, Kepler has struggled to a .219 / .288 / .368 line that works out to 74 wRC+. In 1,771 PAs versus right-handed pitchers, where he has the platoon advantage, he’s produced a much more robust .244 / .331 / .472 line that has been good for 112 wRC+.

The career aggregate numbers mask a story of a young player improving with experience. Breaking it down further, his season by season stats against left-handed pitching illustrate his development.

After struggling mightily against southpaws in his first two full seasons, Kepler started to produce at a passable level in 2018. That season’s line against lefties was better than he fared against right handers (.216 / .318 / .403). Max consolidated those gains and built on them further in 2019, posting 129 wRC+ against left-handers that again outpaced his production against righties (118 wRC+). This new production level was supported by the advanced metrics. Statcast calculated expected numbers estimated .284 xBA, .475 xSLG, and .353 xwoba against left-handers.

Improvements that led to success

Kepler’s early career struggles against left-handers were largely driven by two critical factors - plate discipline and launch angle. In 2016 and 2017, Kepler struck out in 25.6% and 29.2% of his plate appearances against LHP, respectively, while walking 7.5% and 5.1%. These figures were supported by swing and miss rates around 27%-28%. In 2018, Kepler began to show improvements in this area, cutting his strikeout rate to 21.6% and increasing his walk rate to 9.0%. In 2019, he shaved another chunk off the strikeout rate, driving it down to a very good 14.7% while holding his walk rate at 8.0%.

At the same time, Kepler also began to drive the ball in the air when facing left-handed pitching. After averaging a batted ball launch angle of 8 degrees and 7 degrees in his first two seasons, Kepler doubled that average to 14 degrees in 2018. In 2019, he increased that again to 18 degrees. Perhaps as you would expect with better plate discipline and more optimal launch angles against lefties, Kepler’s proportion of batted balls against them that were classified as “hard hit” also spiked, increasing from 21.8% in 2017 to 39.8% in 2018 and staying at 38.7% in 2019. Those higher launch angles meant more high line drives and fly balls, and more productivity in terms of extra base hits. After logging just 16 extra base hits against left-handers in his first two seasons combined, Kepler hit 16 off them in 2018. He followed that up with 16 more (including 9 home runs) in 2019. Those extra base hits and home runs were the main factor in the .519 slugging percentage that stood out in the chart earlier.

Kepler’s success against left-handers coinciding with his breakout 2019 campaign was not a coincidence - his breakout was largely because of his growth in handling left-handers. With his profile rounded out, Kepler’s standing within the league-wide pool of right fielders increased too. In 2019, he ranked 12th of 28 qualified right fielders in wRC+, tied with Nicholas Castellanos and right behind well known offensive forces Bryce Harper and Charlie Blackmon. After two consecutive strong seasons, it appeared Kepler had closed this gap in his game and was following the path of previous young Twins left-handed hitters that grew to be threats against southpaw pitching - Joe Mauer and Justin Morneau.


All of that makes Kepler’s 2020 results much more confounding. His overall line remained passable, but it was significantly below his 2019 level and his performance against left-handed pitching completely cratered. In 53 plate appearances against LHP in 2020, Kepler slashed a paltry .128 / .208 / .170 that rolled up to just 5 wRC+. Yes, five. It was easily the worst performance of his career against same-sided pitching.

On one hand, you might argue that his numbers against LHP were suppressed by bad luck and point to his .171 BABIP off lefties. But that argument can quickly be put to rest by pointing out Kepler’s average exit velocity fell by almost 4 miles per hour (to a very low 86.0 mph) and his Statcast expected numbers estimated only .223 xBA and .287 xSLG versus LHP. Yes, his actual results under performed those peripherals, but the peripherals were pretty terrible. The extra base hits also disappeared. Kepler had only 2 doubles and no homers off southpaws in 2020. More alarming is that he gave back in 2020 the plate discipline gains he had made the previous two seasons - evidenced by his strikeout rate and swing and miss rate against LHP spiking back up to 24.5% and 26.4%. To sum it up, he swung and missed and struck out more; and when he did make contact it was significantly weaker than before.

Looking Forward

As you’ve likely read, and will continue to read throughout this winter, it’s challenging to know what to make of the unusual 2020 season. In comparing Kepler’s season to prior campaigns, we’re dealing with very different sample sizes - just 53 PAs against lefties, slightly less than a third of what he had in each of the prior two seasons. We also don’t know how to quantify the impact of the condensed and bubbled up summer camp on player preparation. Kepler also missed 9 games mid-season with an adductor strain that required a stint on the injured list.

Those are only a few of the many potential explanations that could make Kepler’s 2020 struggles against left handed pitching an aberration that we should overlook. Perhaps with another 100+ opportunities his 2020 numbers against lefties would have straightened out to something more in line with his 2018-2019 levels. Perhaps the odd summer camp format inhibited Kepler from getting comfortable against left-handed pitching in games that did not count before the season. Perhaps the mid-season injury was enough of a disruption to prevent him from finding his groove. Perhaps it was something else. We don’t know.

But the decline was steep enough, and supported by regression in the key fundamental areas that had contributed to his improvement, that it merits re-opening the critical question of whether he can hold his own against same sided pitching. Max Kepler who can hit lefties is a franchise building block. Max Kepler who can’t hit lefties is a liability that needs to be managed around for a team with championship aspirations. None of this is to suggest the Twins might need to move on from Kepler or even adjust his role. He’s still a very good player who should be playing every day. But as the Twins move into the offseason they’ll be seeking ways to upgrade the lineup that finished just 24th in the Majors against left-handed pitching (81 wRC+). How they assess Kepler as part of the solution or part of the problem against lefties will be an important question for the decision makers to answer. Which version of Max Kepler do they believe is the real Max Kepler? The one who can hit lefties? Or the one who can’t?

John is a contributor to Twinkie Town with an emphasis on analytics. He is a lifelong Twins fan and former college pitcher.