Fastballs Keep Pouring Into the Top of the Zone

What a month it has been for pitchers. We witnessed no-hitters by Joe Musgrove, Carlos Rodón and, just yesterday, John Means. Corbin Burnes threw a major-league record number of strikeouts without issuing a walk (49 punch outs and counting, though Burnes is currently sidelined). And Shane Bieber has pitched a multitude of double-digit strikeout games by. Oh, and Jacob deGrom and Gerrit Cole are just toying with hitters. On the flip side, it’s been a dismal start at the plate for most of the game’s hitters, though there are a few exceptions (here’s looking at you, Mike Trout and Vladimir Guerrero Jr.). Last week, Brendan Gawlowski covered April’s .232 league-wide batting average, an historic low. A combination of the highest strikeout rate on record and a below-average BABIP made the first month of the season one to forget for fans of offense and batted balls.

According to an anonymous GM recently quoted in The Athletic, the root of the league’s hitting woes is simple: “Pitching is too good.” The league-wide strikeout rate has been on the rise for several years now, but to see the rate jump like it has in the season’s first month is alarming and worth investigating. Are pitchers just getting better? Are hitters selling out for the long ball? It’s probably a combination of both. To dissect the strikeout problem, let’s look at how batters are striking out and what it reveals about how they are being pitched.

Not all strikeouts are created equal. To start, there are three ways a pitcher can earn a strike: a called strike, a swinging strike, and a foul ball (to keep it simple, I’m considering bunt attempts swings here). Going back to the 2015 season, a clear trend has set in.

Pitch Outcomes 2015-21
Season Balls Batted Ball Events Strikes Swinging Strikes
2021 36.5% 16.6% 46.7% 12.7%
2020 37.0% 16.7% 46.1% 12.3%
2019 36.3% 17.2% 46.3% 12.1%
2018 36.3% 17.5% 45.9% 11.6%
2017 36.4% 17.7% 45.5% 11.3%
2016 36.4% 18.0% 45.2% 10.9%
2015 36.0% 18.6% 45.0% 10.7%
SOURCE: Baseball Savant
*2021 results using pitch data through games played on April 30.

Strikes account for an increasing share of pitches thrown (46.7% compared to 45.2% just five years ago). Included in the table is swinging strike rate (SwStr%), a subset of strikes. Notice that as batted ball events (BBE) decrease, SwStr% increases at a similar rate. Essentially BBE are being traded for strikeouts. The distribution of strikes is also changing, with called strikes and foul balls decreasing a small amount, but SwStr% climbing at a high enough rate that not only does it compensate for the dip in called strikes and foul balls but results in an overall increase in strikes.

The surface-level data is clear; swinging strikes are the root of the elevated number of strikeouts. Plate discipline statistics give us even more insight into what batters are doing with their approach. After peaking in 2019, the league-wide O-Swing% (the rate at which batters chase pitchers outside of the zone) has come back down. It’s sitting at 30.7% so far this season, which is about where it was for 2020. The percentage of pitches in the strike zone (Zone%) and, in turn, the overall swing rate (Swing%) have both gone up as well. What should be concerning to teams and is at the heart of the strikeout problem is the decrease in Z-Contact% (rate at which batters make contact on swings at pitches in the strike zone). The league’s Z-Contact% is currently at 83.3% which is nearly a full percentage point lower than last season’s rate.

Well that was easy, problem solved. Batters are just missing the ball more often because they’re manipulating their bat path through the strike zone to elevate more and increase the launch angle. Not so fast; it’s time to look at what pitchers are doing differently.

Pitchers are throwing in the strike zone more yet batters are striking out more; that’s counterintuitive. More pitches in the zone should result in more contact. To further investigate, let’s look at the distribution of pitches thrown in specific locations inside and outside of the strike zone. Statcast has defined components of the Attack Zone as “heart,” “shadow,” “chase,” and “waste.” We’ll focus on the “heart” zone, which is the middle portion of the strike zone, and the “shadow” zone, which is the area just inside and outside of the border of the strike zone. As far as trends go, there’s not a significant change in the frequency of pitches in any of these zones with one somewhat puzzling exception: more pitches are being thrown in the “heart,” the middle of the strike zone, going from 25.4% in 2020 up to 26.4% through the first month of this season. This is confounding because these are the pitches that hitters typically have the most success making contact with.

The picture clears up a bit when breaking down the early season’s swings and misses by pitch type. There has been little change related to chase rate so far this year; breaking and offspeed pitches outside of the strike zone still tend to get a lot of swings and misses but no more than they have previously. However, fastballs have gained in their share of whiffs thus far, with a SwStr% of 10.4% on fastballs (through games played on May 2) up from 9.7% in 2020.

Swinging Strike Rate by Pitch Type
Season Fastballs Breaking Offspeed
2021 10.4% 15.5% 16.4%
2020 9.7% 15.4% 16.5%
2019 9.5% 15.6% 16.1%
2018 8.9% 15.5% 16.2%
2017 8.6% 15.3% 16.2%
SOURCE: Baseball Savant
*2021 results using pitch data through games played on May 2.

Fastballs have accounted for 47.6% of this season’s swinging strikes. That’s the highest share of swinging strikes by fastballs in the last five seasons, with the second highest of 46% coming in ‘18. What’s even more striking (pun intended) is that fastball usage has dipped a bit in recent years in favor of breaking and offspeed pitches. Pitchers are throwing fastballs with 57.8% of their pitches, which is up from last year but still more than 2% lower than in 2018. Pitchers are being more surgical with their heaters. The fastball up in the zone has become a common out pitch in recent seasons, so it’s not surprising that it’s being used more frequently to generate strikeouts. The swing-and-miss ability of a fastball has been linked with velocity, spin rate, and vertical movement, all of which have consistently increased in recent seasons.

Fastballs with more active spin tend to create more upward movement (or ride). Hitters typically swing and miss underneath fastballs with a lot of ride because the ball appears to rise as it approaches the plate. These pitches are most effective when located in the top of the strike zone. For all the additional swings and misses at the plate, the majority of these are coming in the top part of the “heart” and “shadow.”

Fastball SwStr% by Zone
Season Top Shadow Zone Top Heart Zone All Other Zones
2021 20.1% 19.2% 7.9%
2020 19.0% 16.9% 7.5%
2019 18.7% 16.3% 7.5%
2018 17.7% 14.5% 7.0%
2017 16.3% 14.7% 6.9%
SOURCE: Baseball Savant
*2021 results using pitch data through games played on May 2.

While the table above indicates SwStr% is up on fastballs in all locations so far this season, the most pronounced increases are in these top portions of the “heart” (2.3% increase from 2020) and “shadow” (0.9% increase) areas. Coupled with higher velocities and spin rates, pitchers have been pouring fastballs into the top part of the zone at a higher frequency this season. For hitters, it’s sink-or-swim and many of them are sinking. Earlier, I noted that batters were seeing more pitches in the “heart” zone, which are generally the most likely pitches to barrel and result in the highest wOBA. Batters have whiffed on 19.2% of fastballs thrown in the top third of the “heart” zone, up from 16.9% last season. Yes, pitchers are getting better. Their fastballs have more velocity and ride, but they’re also putting them in the right spot to earn strikeouts.

Hitters as a whole tend to underperform in the first month of the season as it relates to many rate statistics, including batting average and slugging percentage. But this doesn’t show itself as clearly in K% and SwStr%. From 2015 through 2019, batters managed a K% anywhere from 0.2 below and 0.3 above the full season average. If this were to play out for what we’ve seen in 2021 so far, it’s conceivable that SwStr% could come back down a few tenths of a percent. Looking at the table above, the SwStr% against fastballs could return to 2020 levels for some zones, but the top of the zone will remain a more challenging place for hitters to succeed as even an “April” adjustment would leave SwStr% in the top of the strike zone at a very high level.

The secret about active spin and fastball ride has been out for a while now and teams are using this information to further improve effectiveness of their pitching staffs. Through the first month of the 2019 season, a total of 88 pitchers recorded at least 10 four-seam fastballs with a spin rate of over 2500 rpm. In 2021, that number has grown by 35%, with 119 pitchers accomplishing the same feat. The increase in pitch speeds and active spin has come in large part from organizations prioritizing pitchers who possess these characteristics and training them to optimize their effectiveness. Hitters looking to adapt will need to learn to hit the high fastball, or lay off of it when it rides out of the zone, because they will continue to see a lot of it.

Chet is a contributor for FanGraphs. Prior to FanGraphs, he wrote for Purple Row. When not writing about baseball, he is a data scientist and outdoor sport enthusiast. He can be found on Twitter at @cgutwein.

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Mike NMN
2 years ago

Nice analysis, I wonder what a thoughtful MLB front office might do to tweak the rules in a manner that might lead to a little more offense. Or if the author has any suggestions. This is not a good trend.

2 years ago
Reply to  Mike NMN

Expansion and NL DH. Oh, wait, you said “thoughtful.” 😉

Would lowering the mound make it easier, harder, or no change to throw the riding, high-spin fastball?