The Astros were prolific users of the infield shift on defense prior to 2023. Then MLB prohibited most versions of the infield shift in 2023. Based upon the Field Bible’s team stats, the Astros’ Defensive Runs Saved (DRS) was reduced by 27 runs due to the loss of the shift defense (35 DRS in 2022 for the shift defensive alignment minus 8 DRS in 2023 for the more limited shift). This implies that the Astros’ pitching staff lost the equivalent of nearly 3 wins.
I have written several articles about the trend over the course of the season: link, link, and link. Now that the 2023 season is behind us, we have a little more information regarding the impact of the shift rule on Astros’ pitchers.
One of the best articles summarizing the impact of the shift was published by Baseball Prospectus in November, 2023 (“The End of The Shift Helped Lefthanded Line Drive Hitters The Most” Robert Arthur). As a side note, the article appears on the Fangraphs site, along with other nominees for SABR awards. If you are interested in sabermetrics you can review the nominated articles and cast your vote.
Arthur’s article takes a granular approach to league data to identify batted balls which were caught in 2023 but would have been outs with the outlawed shift. The conclusion is captured by the article’s title. Since one of the objectives of the shift was to curtail LH pull hitters, it’s not surprising that two-thirds of the 750 extra hits were attributed to left hand batters. 56% of the extra hits for left handed bats were line drives. According to the article, “the largest increase in hitter success [is] just behind the infielders, in the shallow part of the outfield.”
The interesting conclusion is that the shift’s greatest impact is curbing line drives, and only to a lessor extent ground balls. Over the last decade, writers have been perplexed by the shift because they concentrated on measuring ground ball batting average. Despite seemingly minor impact on ground balls, teams continued to double down on implementing the shift. However, the most significant impact may have been pulled line drives. It made sense to target the shift at line drives, because they provide the highest batting average for the hitter and also produce more extra bases than a ground ball.
The article’s conclusion: “Thanks to Manfred’s rule changes, we got the closest thing to a controlled experiment that baseball permits, and it showed that the shift killed all batted balls on flat trajectories from around -20-25 degrees, the most valuable and common of which were apparently line drives from lefties.”
Since this article confirms that LH line drive hitters are the primary beneficiaries of the Shift rule, we can use this information to examine the probable impact on Astros starting pitchers. I don’t have data as granular as would like, but the data on the pitching splits pages at Baseball-Reference is surprisingly consistent with the conclusions of the B-Pro article. For this comparison, Batting Average on Balls in Play (BABIP) is the most useful metric because it excludes home runs. After all, HR rates are fairly volatile and could disguise the shift impact.
At the league level, comparing 2022 and 2023, LH Pull HIts BABIP increased from .258 to .288. The groundball BABIP (all hitters) increased from .236 to .244 and the line drive BABIP (all hitters) increased from .618 to .641. The OPS+ for LH Pull Hits increased by 10.9%, although perhaps not solely due to shifts.
Comparing the Astros’ pitching staff change in BABIP to the league average also suggests that the Astros’ pitchers were affected by the loss of the shift more than most teams. The Astros’ pitching staff saw a higher percentage increase in batting average for the ground ball and line drive categories than the typical league pitcher.
Increase in LHB Pulled Hit BABIP: MLB .03 points (11.6%); Astros .029 points (10.9%)
Increase in GB BABIP: MLB .008 points (3.4%); Astros .021 points (9.2%)
Increase in LD BABIP: MLB .013 points (2.1%); Astros .048 points (8.1%)
Given that the main impact of the shift rule is to allow more line drives to fall in safely, it is noteworthy that Astros pitchers’ BABIP on line drives increased from well below league average in 2022 (.595) to well above league average in 2023 (.643).
We can perform a similar comparison for the individual Astros’ starting pitchers by comparing the BABIP components for 2023 to 2022. For this comparison, I did not include J.P. France, since he did not pitch at the ML level in 2022.
- The table above shows each pitcher’s change from 2022 to 2023 for LH Batter Pull Hits, as well as Groundball and Line Drive BABIP. Before examining the table, an interesting context is that four of the five Astros starters exhibited reverse platoon splits in 2023. Verlander, Brown, and Urquidy are RHPs who suppressed LH batter OPS more than RH batter OPS. Valdez is a LHP who suppressed RHBs more than LHBs. RHP Javier exhibited traditional platoon splits and is vulnerable to LHBs.
- Urquidy appears to have been the least affected by the Shift rule. This may be due in part to the fact that he is tough on lefthand hitters, which presumably is due to an effective change up pitch. Urquidy improved his performance against LH Pull hits and GBs. However, he allowed an increased BABIP on line drives. That could reflect, in part, the defensive impact of removing the shift. But that conclusion is fairly uncertain, given the improved BABIP on ground balls and LH Pull hits.
- Surprisingly Javier seems to have been significantly affected by the elimination of the shift. I say “surprising,” because Javier is an extreme fly ball pitcher, who only produced 25% ground balls. He and the defense behind him allowed large increases (40+%) in groundball BABIP and LH Pull hit BABIP. Javier’s line drive BABIP also shows an increase which could reflect the elimination of the shift. The high BABIP on ground balls (.331) and LH Pull hits (.359) stand out because Javier normally allows one of the lower Batting Averages Against in baseball (career BAA .199). Javier’s platoon split weakness against LHBs may explain why he was affected more when the shift was eliminated.
- Given his high ground ball rate, Valdez is the pitcher we expected to be harmed the most by the Shift rule. And he definitely shows signs of the defensive impact. But it appears that the impact was more from line drives than ground balls. The BABIP on ground balls declined to .188 in 2023. But the BABIP on line drives increased to .656, and the BABIP on LH pull hits increased above the previous low level in 2022. Despite the imposition of the shift rule, Valdez likely would benefit by improving his GB rate to the league leading grounder rate of 2022.
- The sample size for Brown was relatively small in 2022—so take that as a caveat for his part of this table. But Brown appears to have experienced increases in three of the four measured components, compared to 2022. Although Brown has reverse splits, he showed more vulnerability when left handers pulled the ball in 2023. Brown is a high ground ball rate pitcher like Valdez, but his lower OPS when facing LHBs may have mitigated the adverse impact of the Shift rule. Overall, Brown’s most significant issue is against RHBs (129 OPS+ vs. righties).
- Verlander probably is moderately affected by the elimination of the shift. He was able to suppress line drive BABIP, but ground balls were more likely to find holes in the infield in 2023 (25% increase in Ground Ball BABIP). Although Verlander remained fairly effective against LH pull hits, the BABIP and OPS+ increased noticeably from the low level in 2022.
Some people may have a “so what?” reaction to this analysis. Nonetheless, I am fascinated by the relationship between defensive attributes and the performance of Astros’ pitchers. And hopefully I have shed some light on that subject. Also, this may aid our understanding of what kind of performance we can expect from our starting pitchers in the future. Finally this analysis could lead the pitching staff and coaches to find ways to mitigate the loss of the 2022-style shifts. For example, infield coaches may refine and improve the use of limited shifts allowed by the Rule. The Astros’ limited shifts in 2023 were effective (8 DRS), and more experience with those alignments could lead to more efficient defense.