By Proloy Bhattacharyya
September 12, 2005
Our analysis has consistently shown us that home teams perform better against non-divisional rivals but we have always lumped Interleague teams into this category. There is reason to believe that Interleague home teams have a larger advantage.
It makes sense for home teams to perform better in Interleague play for a variety of reasons. AL teams have an advantage at home and a disadvantage on the road because of the DH. When allowed to use the DH, AL teams are able to use a vastly superior #9 hitter than the NL teams are used to. If AL teams are not allowed to use the DH, this will often cause the AL team to either drop their DH, who is generally one of their best hitters or move him into a position for the Interleague games. Since the DH is not used to playing the position, he becomes susceptible to committing errors.
There is also an issue with familiarity. Road teams in Interleague games are often not familiar with the stadium they are playing in and as a result cannot use it to their advantage. The classic example would be at Fenway Park where banging balls up against the Green Monster leads to a lot of doubles. The Padres had a losing home record last season and much of their complaints had to do with the fact that their hitters were not familiar enough with the stadium to take advantage.
Familiarity can also be extended to pitcher / hitter scouting reports. With both teams lacking the extensive scouting reports they normally would have in normal games, the home field advantage will likely weigh more.
Our analysis shows us that home teams during Interleague play have won 56.2% of the time versus 53.2% during non-Interleague play. A 3.0% difference is significant here, especially in a sport where home field advantage is perceived not to exist.
Home Favorites in Interleague play over the past 3 seasons have gone 331-191 (63.4%) +53 units. If our team is motivated off a loss to the very same team it is facing, our teams win percentage jumps up to 65.1% and the spread is off by about 15 points on average.
As you can see, since Interleague games represent such a small minority of the total number of games played, the home field advantage in such games is not readily known.