Should You Trust Divisional Underdogs in MLB?

Oriole Bird mascot Baltimore Orioles Milwaukee Brewers baseball
The Oriole Bird mascot of the Baltimore Orioles is introduced before the Orioles and Milwaukee Brewers game. Rob Carr/Getty Images/AFP.

If you research successful MLB betting strategies, it won’t take you long to run across the old adage about taking divisional underdogs.

The “Divisional Underdogs” Strategy Explained

Because of baseball’s unbalanced schedules, teams play their divisional foes far more often than teams outside the division, with nearly half of their regular-season games coming against the four other teams that share their division.

That level of familiarity, according to the rule of thumb, means that the worst teams in the division will actually do better against their divisional foes than they will with teams outside the division they’re facing for one of the first times.

The logic makes sense, but …. Is it true?

The Case of the Baltimore Orioles

The New York Yankees have the best record in baseball as we enter the final week of May. A juggernaut, the Yankees are dominating one of MLB’s best divisions, but, in the first month and a half of the season, the Bronx Bombers have suffered three walk-off losses.

Two of them have come against the lowly Baltimore Orioles, who are on pace to finish last in the American League East for the sixth time in the last seven seasons.

Baltimore was a thorn in the Yankees’ side last season, arguably keeping New York from winning the East by beating the Yankees 8 times in 19 games. Baltimore had a .421 winning percentage against the Yankees, .308 against everyone else, seemingly confirming the “divisional underdogs” strategy.

Except the reason that the 8-11 record against the Yankees kept New York from winning the East is that Baltimore went 1-18 against another AL East team–the Rays. Overall, the Orioles went 20-56 against the four teams in the East, for a .263 winning percentage. Against the other five divisions, Baltimore went 32-54, .372, 100 points better than against the teams it knew the best.

Why It Doesn’t Always Work?

It turns out that, while the worst teams become more familiar with their divisional foes, the best teams in the division also become more familiar with them.

Indeed, the 2021 performance against the Yankees appears to be the outlier for the Orioles, who went 3-7 against New York in 2020 and 2-17 against them in 2019.

This year, Baltimore is 7-12, .368 against the East, 10-13, .435 against everyone else.

Other Similar Cases

The Washington Nationals are in last place in the National League East, and the Oakland A’s are at the bottom of the American League West, both with sub .400 winning percentages.

Both teams have shown the same pattern as the Orioles. The better teams in their divisions seem to know them well, and they’re in better positions roster-wise to match up with the bottom dwellers and dominate them. Washington is 5-11, .313, against the rest of the NL East and 9-17, .346 against everyone else. Oakland is 3-7, .300 against the AL West and 14-19, .424, against the other five divisions.

Last year, the Arizona Diamondbacks matched the Orioles with the worst record in baseball, at 55-110. And, like the Orioles, the D-Backs were steamrolled by the contenders in their own division. Arizona went 22-54 against the NL West for a .289 percentage. Against the rest of the world, they went 30-56, .349.

Last season, the two worst teams in MLB were 30% more likely to beat a team outside their division than inside, showing that unfamiliarity breeds upsets.

Real-Life Examples

Of course, there are some teams that offer support to the adage. The Reds were off to a historically bad start to this season before getting on track by knocking off their divisional rivals, the Pittsburgh Pirates. Cincinnati is 7-9, .438, against the National League Central this season, 5-19, .208 against the other five divisions.

Kansas City and Detroit are tied for last in the American League Central, but both have been better in the division than out. The Royals are 9-12, .429 against the division, 5-14, .263 against the rest of MLB. The Tigers are 4-7, .364 inside the division, 10-19, .345, outside.

The Conclusion

So, what can we gather from all of this information? Well, don’t believe everything you read.

There’s plenty of data out there, so if you get a “rule of thumb” for your MLB betting that’s easy to research, it’s worth taking a few extra minutes to look into it before accepting it as gospel.