Why is Max Kepler Hitting Well, but Not Hitting Home Runs?

Over 35 games played, Twins right fielder Max Kepler has garnered 131 plate appearances. Due to missing 13 games from a right knee contusion that placed him on the 10-day IL and five rest days, Kepler is not among the team leaders in plate appearances. However, the 31-year-old is among qualified team leaders in numerous offensive metrics:

• 2nd in Isolated Power (ISO) - .214
• 1st in Batting Average (BA) - .291
• 2nd in On-Base Percentage (OBP) - .354
• 2nd in Slugging Percentage (SLG) - .504
• 2nd in weighted On-Base Average (wOBA) - .372
• 2nd in wRC+ - 144
• tied-2nd in Wins Above Replacement at FanGraphs (fWAR) - 1.3

Kepler has been the Twins' best offensive player (alongside catcher/designated hitter Ryan Jeffers), and he is doing so while excelling against both left- and right-handed pitchers. Here are the hot-hitting lefty's splits to begin his 2024 campaign:

• vs. LHP - .381/.409/619, 22 plate appearances, eight hits, two doubles, one home run, one walk, four strikeouts
• vs. RHP - .271/.343/.479, 109 plate appearances, 26 hits, 11 doubles, three home runs, 10 walks, 16 strikeouts

Kepler has shined against same-handed pitchers, although (so far) only in a very small sample of opportunities. Moreover, his good fortune in limited plate appearances suggests that the Germany native is improving in an area in which he has struggled most of his career (.220 career BA over 1,021 plate appearances against left-handed pitchers). Kepler has always hit well against right-handed pitchers (.244 career BA and 131 home runs over 2,962 plate appearances), yet he is exhibiting enhanced results this season. Being in a great place mentally, reducing his leg kick, and good health have been cited as reasons for the long-time Twin's offensive renaissance, which really began last July. However, there is one difference between Kepler's success in the second half of last season and early this season: his number of home runs.

During the second half of the 2023 season (July 14 through October 1), Kepler hit 12 home runs while generating a .243 ISO over 265 plate appearances. Interestingly, he has hit only four home runs over 123 plate appearances this season, despite sporting a similarly well-above-average .220 ISO. Why is Kepler's power not translating to home runs? Let's take a look.

Lack of Exit Velocity at Higher Launch Angles
Kepler's hardest-hit balls are being manufactured at launch angles that prevent hitters from getting the ball over the fence. When Kepler hits the ball at a 25- to 35-degree launch angle, he's sporting a 69.9 MPH 10th-percentile Exit Velocity (EV) and 102.1 MPH 90th-percentile EV. At a 35- to 45-degree launch angle, he has a 77.6 MPH 10th-percentile EV and a 97.1 MPH 90th-percentile EV. Balls hit in this exit velocity range can sneak over the wall when the conditions are especially favorable, but they're mostly flyouts or doubles, depending on the ballpark. Kepler's inability to hit balls with a 25- to 45-degree launch at especially high EVs provides insight into why he has been unable to hit more home runs.

Despite not being able to generate the EV numbers necessary to lift balls with a launch angle between 25 and 45 degrees over the fence, he is hitting balls in lower bands exceptionally well. When hitting it at a launch angle between 5 and 15 degrees, Kepler generates an 84.8 MPH 10th-percentile EV and a 110.8 MPH 90th-percentile EV. Between 15 and 25 degrees, the numbers are: 85.2 MPH 10th-percentile, 107.1 90th-percentile EV. 

Kepler performs exceptionally well when hitting the ball at a launch angle between 5 and 25 degrees, evidenced by a combined .782 xWOBA. For reference, when hitting the ball at a launch angle between 25 and 45 degrees, he is manufacturing a less inspiring .337 wOBA. This is true of most hitters. On average, the league's best outcomes come between 2 and 25 degrees of launch angle. Unfortunately, lifting the ball over the fence at this angle is much more complicated than if he could generate a higher EV on balls hit at a launch angle between 25 and 45 degrees. That's what separates the league's great power hitters from the rest.

Baltimore Orioles star shortstop Gunnar Henderson (tied for most home runs in MLB with 17) is performing at a similar rate as Kepler within the 15-to-25 band. Here is how the two compare:

• Kepler - .851 xWOBA, 1.500 SLG, 98 MPH EffVel, 85.2 MPH 10th-percentile EV, 107.1 MPH 90th-percentile EV
• Henderson - .835 xWOBA, 1.474 SLG, 99 MPH EffVel, 90.6 MPH 10th-percentile EV, 109.1 MPH 90th-percentile EV

Although Henderson is generating a faster Effective Velocity, 10th-percentile EV, and 90th-percentile EV than Kepler, the two are producing at similar rates when fitting into that range, evidenced by their respective slugging averages. However, the Orioles' young shortstop separates himself from the Twins' veteran right fielder when it comes to their productivity when hitting the ball at a launch angle between 25 and 35 degrees. Here is how the two compare:

• Kepler - .639 xWOBA, 1.286 SLG, 75.8 MPH EffVel, 69.9 MPH 10th-percentile EV, 102.1 MPH 90th-percentile EV
• Henderson - 1.222 xWOBA, 2.857 SLG, 88.7 EffVel, 91.1 MPH 10th-percentile EV, 108 MPH 90th-percentile

Despite performing well and still generating positive results when hitting the ball between 25 and 35 degrees, Kepler is generating a lower EV, resulting in more hits worth one or two bases and more flyouts. Conversely, Henderson is maximizing the velocity of the balls he hits between 25 and 35 degrees. Thus, they're clearing the fence. 

Another indicator of Kepler's inability to launch the ball over the fence at the rate you'd expect is his Well-Hit Launch Angle (Well-hit LA), which measures a player's launch angle when hitting the ball with a 95 MPH or greater EV. Kepler's Well-Hit LA is below average, residing at a 42nd-percentile 10.9 degrees. In contrast, Kepler's Well-Hit LA in 2019 (his best offensive season) resided at 12.7 degrees. He is making a lot of contact and putting the ball into play at a high rate. However, his hardest-hit balls don't have much air under them, resulting in flyouts, singles, and doubles rather than home runs.

Research assistance provided by TruMedia Sports.