The 2023 MLB season starts today. Baseball bettors have another 2,430-game slog ahead, one surely filled with peaks and valleys. One way to get a leg up during the grind, perhaps, is to enter it with full knowledge of how 2023 MLB rule changes may affect the betting landscape.
Last season brought significant changes with the universal DH and expanded playoffs. Those definitely affected baseball betting — for example, the Phillies wound up making the World Series out of a No. 6 seed that didn’t previously exist. For 2023, even more controversial rules have been changed or introduced. This year, we’ll see larger bases, pitch clocks, and restrictions on defensive shifting and positioning.
Let’s take a look at what these MLB rule changes could mean for bettors. As an addendum, we’ll see if any relevant park changes should factor into bettors’ thinking as well.
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2023: Year Of The Over?
The 2022 season proved to be the year of the under, at least early on. Games consistently stayed under as markets wildly overestimated run scoring, likely due to the dead baseball in use. It took more than a month for that to correct, so bettors could simply blanket bet unders for an extended period and print money.
For 2023, many are licking their chops to fire overs instead, with simple and obvious reasoning.
For starters, controlling the running game has become more difficult. Six inches has been lopped off on the distance between the non-home bases — three on each end. Six inches may not sound like a lot, but think about how many bang-bang plays occur on steals and sprints to first. More of these runners will remain live to potentially score runs, and they’ll get closer to home more often.
Plus, pitchers have a reduced ability to hold runners via pickoffs. Each pitcher may only attempt to throw over — or even disengage the rubber and fake a throw — twice per plate appearance. Any further attempt remains legal, but it advances the runner if it fails.
Perhaps more enticingly, the limitations on defensive shifting should turn some outs into baserunners as well. At least, that’s the way the thinking goes. For 2023, when the pitcher releases the ball, the defending team must have four infielders with at least one foot on the dirt, and two must occupy either side of 2B.
So, bet overs and print?
Don’t Overreact To Defensive Shift Ban
Not so fast.
First, keep in mind that almost 70% of plate appearances last year saw no shift whatsoever, according to one source. So, only a fraction of plate appearances are even affected by this MLB rule change.
And if you’re expecting to see a steady stream of singles hammered on the ground into right field by lefties, think again.
Consider that according to research by Justin Choi at FanGraphs last year, the league-wide BABIP (batting average on balls in play) was .293. Previous seasons generally hovered around .298, including 2013, when shifting was barely a thing. That’s a difference of five hits per 1,000 balls in play. Research by Kyle Glaser at Baseball America came to a similar conclusion: the shift ban in the minors had no meaningful effect.
Lefties will likely face some variation of a legal shift still anyway. Plus, teams are now more incentivized to play rangier defenders in the infield, where they may previously have hidden big bats out there with the expectation that the shift would reduce the impact of their defensive shortcomings. Hi, Max Muncy.
Here’s a chart showing runs scored per game the past five full baseball seasons:
| Year | Runs Per Game |
|---|---|
| 2017 | 9.3 |
| 2018 | 8.9 |
| 2019 | 9.7 |
| 2021 | 9.1 |
| 2022 | 8.6 |
Now, before I go on, I want to first say that I have no idea to what extent the MLB rule changes have been factored in to publicly available projection systems at FanGraphs and Baseball Prospectus. It’s possible the answer is “not at all.” But, here is where each system projects runs per game for 2023.
- FanGraphs: 8.7
- Baseball Prospectus: 8.6
The computers expect negligible difference and I have to say that given the numbers around these MLB rule changes, it’s hard to argue.
Bookmaker’s View
BetMGM Sportsbook’s Christian Cipollini agreed to share views from the other side of the counter on what the rule tweaks will do to betting markets. It sounded like the braintrust dealing with markets and risk there has taken a wait-and-see approach.
“For totals, we’ve been setting as normal with a slight skew towards the over, but mostly just reacting on what we see,” he said. “At BetMGM we will respect the bets we see from our sharp customers and adjust where needed.”
Same deal with player props, it sounds like. While certain hitters (Corey Seager has been frequently mentioned by various media as a player who lost a lot of hits to the shift) stand to benefit more than others, Cipollini said the book will just monitor for unusual betting activity.
“If we see a player being targeted, we will adjust there.”
Stolen Base Spike And Prop Markets
One thing that seems certain is we’ll see more stolen bases this year. Steals have been declining for years as the game shifts more and more toward power, marginalizing the value of gaining a single base. What’s the use in stealing second if the next guy is going to hit a home run or strike out anyway?
According to Jeff Passan, runners in spring training attempted 0.8 more steals per game than they did in the prior spring. Stolen bases are generally successful around 75% of the time. Given that, and looking back at stolen base levels in prior decades, we’ll probably see about one extra steal every other game.
That should produce a negligible effect on total scoring.
More interesting might be what it does to prop markets. Individual players could see some large jumps in stolen base counts. Since many high-profile players will have markets on whether they’ll steal a base, bettors could find some edges here, especially early on.
Watch for which teams and players are most aggressive early on. Additionally, see which teams and pitchers are having trouble keeping runners in check. I say pitchers because some research at Beyond The Box Score (RIP) indicates pitchers actually have more influence controlling the running game than catchers. Under the new constraints, that may prove even more true as delivery time will become crucial.
Along that line of thought, this list from Razzball showing which pitchers have been stolen on most frequently and successfully in recent years could prove useful.
Bookmaker’s View
Cipollini called the stolen base markets “the juicy one.” Indeed, early running action has lit up certain box scores. The Red Sox notably watched helpless as the Orioles ran wild on them, racking up 10 steals (zero caught stealing) in the weekend series.
On Twitter, Jeff Passan shared the following numbers comparing steals in the first four games of the past two seasons:
- 2023: 70 of 84 (83.3%)
- 2022: 29 of 43 (67.4%)
“In general, there has been a blanket nuking of the odds across the board when it comes to steals,” Cipollini said, referring to the extreme shrinking of odds. “Last year you could get most players at +1100, some even higher. That will not be the case this year. Faster players like Trea Turner will see significant changes from this year to last year. Will be a learning curve for the book early one, but ideally after a few weeks we should be well adjusted.”
A few weeks is plenty of time for bettors to hunt down some value, but the clock is already ticking.
MLB Park Changes
Last year, we warned bettors to be ready for a decrease in run scoring at Camden Yards. The impact of the park’s new dimensions turned out to be massive. According to Baseball Savant, the park went from a Park Factor of 110 — the most offense-friendly park in the league in 2021 — to 97, which ranked 24th.
Could bettors see similarly drastic moves at the following parks? Keep in mind that park factors can take years to stabilize, so you’ll be taking some risk thin-slicing it and betting based on early trends.
Comerica Park – Detroit Tigers
For years, fly balls have fallen into far too many fielders’ gloves at Comerica Park. Detroit’s park has consistently produced some of the worst results on barreled baseballs, creating large differences between expected and actual production for even powerful sluggers like Miguel Cabrera and Nick Castellanos. Comerica’s home run factor of 75 in the most recent three-year stretch ranks dead last.
The Tigers’ changes are the most sweeping and probably most impactful:
- Moving the center field wall in about 10 feet
- Cutting the height of the walls in right field from 13 feet in some spots and 8 1/2 in others to a uniform 7 feet
- Moving right field wall in 2 feet
- More padding added to walls to help outfielders make safe catches
Obviously, the last one helps the defense a bit, but overall, we might see a decent boost in offense here. Power hitters from the left side get the most gains. They experienced the majority of the home run shortfall, with a stunning 63 park factor there. Lefty-heavy lineups with a lot of power are the ones to watch for most here.
Rogers Centre – Toronto Blue Jays
Right-center field will have the biggest change as Toronto drastically reconfigured its outfield. The fence will move in 16 feet, but the wall will be raised a little more than 4 feet. Left-center moves in seven feet with the wall raised about 1 foot.
Down the lines, the left-field wall will be raised from 10 feet to 14 feet, 4 inches. Down right, it will be raised from 10 feet to 12 feet, 7 inches.
The power alleys between left-center and center and right-center and center will also have some small changes. On the left side, the wall will come in 2 feet but be raised to 12 feet, 9 inches from 10 feet. On the right, it will come in 11 feet while going from 10 feet high to 10 feet, 9 inches.
Dead center will cut 2 feet off the wall, going from 10 feet to 8 feet.
Overall, it looks like the net effect may be fewer home runs here, although lefties may have an easier time than before. It might just play close to neutral all around. Rogers Centre has been almost exactly neutral in the most recent stretch (99), but right-handers have had it much better on the home-run front with a 114 factor to lefties’ 87. The Jays have (probably not coincidentally) loaded their lineups with right-handed power before this year, bringing a bit more balance with Daulton Varsho, Brandon Belt and Kevin Kiermaier.
Citi Field – New York Mets
A 50-foot section of the right-field wall will be moving 8 1/2 feet in. That should enable left-handed hitters to have a bit more impact power. Right-handers who give up a lot of powerful contact to lefties should be downgraded a hair here. For example, Mets right-handed pitchers Tylor Megill has allowed a .568 slugging to lefties in his career.
Citi Field has played solidly pitcher-favored, generally ranking in the bottom 10 parks for hitters. Last season, its three-year rolling park factor ranked 26th for hitters, meaning it was fifth for pitchers, per Savant.
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