Seven Ways MLB's New Rules Changed The Way The Game Was Played In Spring Training
Major League Baseball enacted a sweeping series of rules changes for 2023 aimed at creating a shorter, more action-packed product.
All the new rules were tested first in the minor leagues. The biggest changes coming to MLB this year are the implementation of a pitch clock, a limit on the number of pickoffs, a restriction on infield shifts and the installation of larger bases.
Only time will tell how these new rules will affect the game, but spring training may give us a preview of what's ahead. In this piece, we compared key rates at spring training this year with spring training last year. We highlight seven significant changes—and one constant. Results are presented in descending order of magnitude.
Caveat: spring training 2022 and 2023 make for imperfect samples. This year, many of the top MLB players, particularly hitters, left their clubs to participate in the World Baseball Classic. Last year saw full participation by MLB players, but they played a shorter-than-usual spring schedule caused by the lockout that delayed Opening Day by a week.
Stolen base attempts per nine innings
The majority of MLB’s rules changes are aimed at stimulating action on the bases. The pitch clock, pickoff limitations and larger bases all create more favorable basestealing conditions—facts not lost on baserunners this spring.
The rate of stolen bases attempted per nine innings increased from 0.80 per nine innings in 2022 to 1.13 at spring training this year. That is an increase of more than 40%, easily the most drastic change to the way the game was played year over year.
The total number of baserunners per game was nearly identical in both years, so this is not a case of more opportunity. In fact, the estimated takeoff rate for runners on first base increased from 8.4% in 2022 to 11.3% in 2023. That rate is up nearly 35%.
Home run rate per nine innings
MLB sought to encourage more balls in play, more basestealing and more athletic defensive plays with its series of rules changes. Home run rate was expected to be largely unaffected, but that wasn’t the case this spring.
The rate of home runs hit per nine innings decreased by 20% year over year, from 1.43 last year to 1.14 this spring training. The home run rate per 100 batted ball events decreased from 5.5 to 4.5, a decrease of 18%.
There is no tidy answer as to why this change occurred. The potential reasons are myriad.
• The characteristics of the ball may be slightly different.
• The pitch clock may advantage pitchers, resulting in hitters feeling rushed by the faster tempo.
• There might have been a measurable talent drain on overall spring training hitting talent because of the World Baseball Classic.
This one bears more scrutiny during the regular season.
Isolated slugging percentage
The rate of extra bases gained per at-bat decreased by nearly 12%, all of it attributable to fewer home runs. The number of extra bases gained via doubles and triples actually increased this year compared with last, going from 8.8 per 100 batted ball events to 9.0 this year.
As with the fall in home run rate, the increase in walk rate will bear watching. It went from 8.7% in 2022 spring training to 9.5% this year.
The reasons for this change are not clear. Perhaps it is a case of pitchers bearing the onus of the new rules and losing a bit of precision now that they’re faced with a pitch clock, shorter rest periods, limits on pickoff throws, the distraction of emboldened basestealers and the threat of an automatic ball.
Stolen base success rate
Stolen base attempts spiked by more than 40% this spring compared with last spring training. The rate of successful attempts made it worth it.
The stolen base success rate increased from 73% last spring to 79% this year. This is notable in the sense that MLB basestealers had already seemingly perfected the art of stealing safely. The three highest success rates of the live ball era are 2021 (75.7%), 2022 (75.4%) and 2020 (75.2%).
Runs scored per nine innings
The overall spring training run-scoring environment was remarkably stable from one spring training to the next. The rate of runs scored per nine innings decreased marginally from 5.44 to 5.24.
Batting average on balls in play
The rate of hits on balls in play increased from 31.2% to 31.8%, a small change in light of the shift restrictions in place this year.
A couple caveats could be in play here:
• The spring training BABIP could have been depressed slightly for the same reasons home run rate was down—a hitting talent drain caused by the WBC and the novelty of the new pace-of-play rules.
• The spring training BABIP in 2021 was .310, so in a broad sense going from roughly .310 to roughly .320 could be significant. Or it could be noise.
Changes to the game the past few years, both organic and via rules changes, have lowered the MLB strikeout for two consecutive seasons. Perhaps 2023 can extend the trend to three in a row.
The spring training strikeout rate was an identical 23.9% in both 2022 and 2023. So despite big changes to the rates of stolen bases and home runs, the number of at-bats ending in strikeouts held steady.
If these spring stolen base and home run trends hold into the regular season, then MLB will almost assuredly shrink its strikeout rate from 22.4% last season. All the incentives will be in place to put the ball in play: more bases gained via doubles and triples, higher hit rates on balls in play, higher stolen base success rates and lower home run rates.