How to Bet MLB Interleague Play

How to Bet MLB Interleague Play

During the 1997 MLB season, teams from the American League and National League competed in regular season competition for the first time in the long and illustrious history of Major League Baseball. Many baseball purists believe the home team gains an unfair advantage, and it’s a valid argument. After all, American League pitchers don’t take batting practice and National League team’s don’t shell out top dollar for designated hitters. This has led many bettors to believe home-field advantage provides bettors with additional value during Interleague Play. Those bettors are sadly mistaken.

After examining every Interleague game since the start of the 2005 season, I found that home teams have gone 1,771-1,468 (54.7%) straight up. However, moneyline bettors would have actually lost -38.08 units by wagering on every home team during Interleague Play.

  • American League home teams: 968-653 (59.7%) with +67.56 units won
  • National League home teams: 803-815 (49.7%) with -105.64 units lost

American League teams have been far more profitable than National League teams, but that’s true regardless of venue. By fading NL home teams during Interleague Play, bettors would have gone 815-803 with +70.04 units won. That means that AL teams have combined to go 1,783-1,456 (55%) with +137.6 units won over the past twelve seasons.

The table below displays the record of AL teams during interleague play since the start of the 2005 season. (Records valid as of April 27, 2017)

DescriptionRecordUnits WonROI
2005136-1164.972.0%
2006154-9839.6915.7%
2007137-1157.202.9%
2008149-10331.5912.5%
2009138-11410.284.1%
2010134-1182.300.9%
2011131-121-3.61-1.4%
2012142-11017.296.9%
2013154-146-7.24-2.4%
2014163-1379.383.1%
2015167-13317.235.7%
2016165-1356.992.3%

As you can see, there have only been two seasons in our historical database where it hasn’t been profitable to take every American League team during Interleague Play. We would never recommend blindly betting on every AL team, but this does reveal an interesting trend. American League teams have dominated their non-conference opposition, but it’s only a matter of time before oddsmakers adjust their lines.

Over this twelve year stretch, the AL team has closed as the favorite in 1916 of 3239 (59.15%) of all interleague games. As they continue to dominate, the perceived advantage for AL teams continues to grow. This can be easily demonstrated by our public betting trends.

Since 2005, the American League team has received the majority of moneyline bets in 58.4% of all games including 81.4% of games where they closed as the favorite. For comparison, National League favorites have received the majority of moneyline tickets in 76.5% of all interleague games. Despite that success, public bettors have been backing the AL at a fairly consist clip.

The table below displays the percentage of games where the majority of moneyline tickets backed the American League during Interleague Play.

YearPublic on ALGamesPercentage
Overall1892323858.43%
200514325256.75%
200616825266.67%
200714525257.54%
200816725266.27%
200914825258.73%
201012825250.79%
201114725258.33%
201214825258.73%
201316630055.33%
201417830059.33%
201516330054.33%
201617430058.00%
2017172373.91%

These American League favorites haven’t just been winning, they’ve been winning big, which had led to impressive returns for runline bettors. Since 2005, AL teams have gone 1,748-1,552 (53.0%) with +171.78 units won in interleague games, and runline favorites have been particularly profitable.

  • AL runline favorites: 901-1,051 (46.2%) with +107.03 units won and a 5.5% ROI
  • AL runline underdogs: 847-501 (62.8%) with +64.74 units won and a 4.8% ROI

Taking American League teams on the runline (5.2% ROI) has been more profitable than taking them on the moneyline (4.2%), which provides bettors with another consideration when handicapping interleague games. It’s also worth noting that the under has historically been very profitable, however, that edge is starting to fade.

Since 2005, the under has gone 811-744 (52.2%) in AL ballparks and 791-751 (51.3%) in NL ballparks. Not surprisingly, my research also found that the average total at an AL ballpark (8.64) was higher than it was at NL ballparks (8.34). That’s particularly interesting because the 12 highest interleague totals were all played at Colorado’s Coors Field — a National League ballpark.

Overall the under has gone 1,602-1,495 (51.7%) during interleague play, but we’ve seen that trend change in recent years. From 2005 to 2014, interleague unders went 1,318-1,187 (52.6%). Over the past two-plus seasons, the under has gone just 284-308 (47.9%). Oddsmakers are always adjusting their lines to account for recent trends and public perception, and it appears that the value taking the under during interleague play.

For more information about how sportsbooks treat interleague games, I spoke with Scott Cooley, a spokesman for Bookmaker.eu. “We do shade them toward the AL a very small amount,” stated Cooley. “There is a perception that the AL is superior to the NL. This is likely because many of the high-profile, big-market teams reside in the AL, and the public perceives the lineups are more potent from top to bottom because of the designated hitter.”

There’s no doubt that American League teams have had a significant advantage since the inception of interleague play, but public perception has caused oddsmakers to shade their lines to encourage action on their National League opposition. Assuming that public bettors continue to hammer American League teams, it will be interesting to see whether they continue to post positive returns over the coming seasons.

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David Solar

David is the Content Manager at Sports Insights. He specializes in sports betting analytics and creating data-driven betting systems.

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