The Impact of Baseball Rules on Oddsmakers’ Lines

As the 2023 Major League Baseball (MLB) season kicked off, three new rule changes were implemented, including a pitch clock, with varying effects on oddsmakers’ lines.

Last year, MLB saw the lowest average runs scored per game since 2015 at 8.57, signaling a decline in offense. In response, MLB Commissioner Rob Manfred introduced three rule changes aimed at increasing scoring. The first change involved making the bases larger, reducing the distance between them by 4.5 inches. This has resulted in an increase in stolen bases to an average of 1.4 per game, up from 0.6, with a higher success rate of 85% compared to 67.4% last year.

The second rule change was the elimination of the infield shift, and early results have shown an improvement in batting averages, with a rise from .230 to .246 in the first four games of the season.

However, despite the uptick in offensive numbers, oddsmakers have not rushed to adjust their lines. Many operators have taken a cautious “wait and see” approach, with some seeing the changes as potentially offsetting each other. For example, the introduction of the pitch clock, which requires pitchers to throw within 15 seconds with bases empty and 20 seconds with a runner on base, has not yet shown a direct correlation with increased scoring.

One area where oddsmakers have made adjustments is in prop bets on stolen bases. With the larger bases leading to more steals, some sportsbooks have moved their lines from an over/under of 50.5 to 52.5 after the first four games of the season, as some players have already accumulated four stolen bases.

Despite mixed results on oddsmakers’ lines, Commissioner Manfred has expressed satisfaction with the early returns of the rule changes, citing positive fan reactions to the faster pace and increased action on the field.