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Tommy Henry.
Tommy Henry.
Photo by Chris Coduto/MLB Photos via Getty Images

Exit velocity is important.

A subtle indication of the importance of exit velocity is that instead of one measurement for it, on-line there are many measurements of exit velocity (maximum, average, average adjusted (for ballpark), and average of the softest/hardest half of balls in play).

A second indication of the importance of exit velocity is that someone built a model to determine expected exit velocity and compare expected exit velocity with actual exit velocity.

A third indication of the importance of exit velocity is that it is a big part in determining something widely important - expected batting statistics (xBA, xSLG, and xwOBA).

There is more to batting success than just exit velocity; batting is a complex process. Nevertheless, at the core, there is an underlying truth – more success happens when the ball is hit hard instead of soft. The following quote has two important points – some batters (even those who hit the ball hard) are not aware of its importance, and it’s a factor that separates the best batters from the rest.

“I think every player who’s ever played the game has cared about exit velocity, whether they know it or not. Right? Every batted ball that’s ever been hit has had an exit velocity and has impacted performance. It’s definitely a separating factor. You need to be able to hit the ball hard to control your luck as best you can. There are a lot of good defenders out there, and oftentimes not a lot of space, so obviously the harder you can hit the ball, the better.” — Nico Hoerner interviewed by David Laurila

Diamondbacks’ Batters.

For Diamondbacks batters, the following table shows SLG and some statistics for ball-in-play exit velocity. Foul balls are excluded from the calculations.

2023 Season. Data from Baseball Savant.

Of those batters with above average SLG, only one has an average exit velocity less than average – Christian Walker. Is this an early/advance indication of the falling part of aging curve. Looking deeper – his maximum exit velocity and the average of his hardest hits were above average. His softest hits were far enough below average that it dragged donw his overage average to below average. My view is it is not an indication of the aging curve. Instead, perhaps it is an indication that he is swinging for the fences.

In the postseason, his exit velocity increased from 88.0 to 91.6 MPH, which was above average. However, instead of improving, his SLG fell from .497 in the regular season to .350, which was below average. My view is that Walker was hitting better in the postseason, but his SLG fell due to a small sample size (his SLG would have increased dramatically with more playoff games).

The table of postseason exit velocities follows. Batters with less than 10 BBE were excluded.

2023 Postseason. Data from Baseball Savant.

In the regular season and the postseason, Ketel Marte had above-average exit velocity and SLG. He is a great example of a batter who is better than average because he hits the ball hard.

Next season, Eugenio Suarez’s batting will bounce back strongly – certainly to the 80th percentile of the ZiPS projection. His 90.3 MPH average exit velocity was the third highest of the Diamondbacks. Last season was a one-time slump in SLG - his SLG was significantly higher in each of his career seasons except his rookie season (2014). Next season, his SLG will return to its usual level.

In the regular season and the postseason, Emmanuel Rivera had above average exit velocity and below average SLG. He has potential to be one of the Diamondbacks’ best batters, but he will not reach that point until something is fixed. Two possible reasons were provided by DBacksEurope, who wrote that he hit too many grounders, and that he hit fastballs poorly.

Diamondbacks’ Starting Pitchers.

Pitchers have two skills that prevent batters from hitting the ball hard. One is deception – an inherent unpredictability of the balls movement, speed, and location. The other is when a pitchers’ strikes cross the plate in the shadow zone (edges of the strike zone) instead of the heart of the plate. However, those skills are easier to talk about than to execute consistently.

For Diamondbacks starting pitchers, the following table shows ERA and some statistics for ball-in-play exit velocity. Foul ball velocities are excluded from the calculations.

2023 Season. Data from Baseball Savant. Regular season average velocities from Baseball Savant’s EV Leaderboard, which differed slightly from Baseball Savant’s average EV. Playoff average velocities calculated from raw data provided by Baseball Savant. Results differed slightly from Baseball Savant’s average EV for unknown reasons.

Surprisingly, Zac Gallen was not at the top of the table. Three possible explanations follow:

  • Perhaps he had an off-year falling out of contention for the Cy Young.
  • Perhaps his work load increased too fast (89% increase in PAs between 2021 and 2023. See the following table for batters faced, and average exit velocity.
Zac Gallen. Data from Baseball Savant.
  • Perhaps Gallen’s mix of pitches included a lot of fastballs, but their batted-ball higher velocities are compensated for by a high strike out rate (he and Kelly were the starters with the highest strikeout percentages of 9.4% and 9.5% per Baseball Reference).

Tommy Henry and Eduardo Rodriguez had the best exit velocities, and therefore they were at the top of the table (with Kelly and Pfaadt close behind). Although it was a small sample size, Henry and Rodriguez had softer average exit velocities in the playoffs and their ERAs were better in the playoffs (showing the importance of exit velocity). My view is that although Tommy Henry is one of several pitchers competing for the fifth spot in the rotation, his excellent exit velocity a strong indication that he will start the season in the rotation.

Summary.

Batted ball exit velocity is important. Observations about Diamondbacks follow:

  • In the regular season, Christian Walker’s exit velocity was below average. My concern was reduced because in the postseason his exit velocity was above average.
  • Ketel Marte is a great example of a batter who is better than average because he hits the ball hard.
  • Eugenio Suarez’s batting should bounce back strongly because of his 90.3 MPH average exit velocity.
  • Emmanuel Rivera has potential to be one of the best Diamondbacks batters, based on his exit velocity, if he changes the right thing. That change might be hit less ground balls, or it might be hit fastballs better.
  • Tommy Henry’s soft exit velocity is a strong indication that he will start the season in fifth spot of the rotation.
  • Zac Gallen’s exit velocity increased, which could be a concern. There are several possible explanations.