The Yankees have clearly built a team that can capitalize on their odd home park – with left-handed power and left-handed starters to limit the other guys’ left-handed power. It is no great surprise that they – over the course of the regular season – won more home games than anybody else. It comes as a greater surprise that the Detroit Tigers finished second in home wins with 50. This is particularly odd because the Yankees were a decent road team, while the Tigers were pretty terrible. In terms of the size of their home/road winning percentage split, the Yankees are tied for 9th in the MLB while the Tigers are 4th [winning 62% at home and 47% on the road].
The source of the abnormally large home field advantage for New York is logical – for the Detroit Tigers it is not. They don’t play in thin air, they don’t force visiting teams to endure jet lag and they don’t appear to have put much effort into crafting a team to take advantage of the spacious outfield of Comerica Park. Playing there prioritizes outfield defense – and this year (as in the past) Tigers corner outfielders are among the worst in the league, statistically speaking.
Comerica Park, due to those big gaps in the outfield, has also had the effect of raising batting-average-on-balls-in-play and favoring line drive hitters. The Tigers do appear to have an offense built around BABIP – but this year their home BABIP is actually slightly lower than on the road. Nonetheless: Tiger hitters have put up an OPS of .793 in Detroit this year as opposed to .722 everywhere else, leading to an average of 4.85 runs per game at home and only 4.11 on the road. So what accounts for the difference? In terms of offense, it’s the propensity to strike out, to hit into double plays and (counterintuitively) to hit home runs. It is possible that those extra double plays on the road are just a matter of luck – the Tigers haven’t shown any propensity to hit more grounders on the road and you’d expect (all else equal) for the reduction and strikeouts and the increase in OBP at home to lead to more GIDP and not fewer. It’s also possible that more favorable counts are giving the Tigers (logically) fewer strikeouts and also better pitches to hit (leading to more jacks and fewer giddy-ups).
Of course Tiger home field advantage isn’t just offense, it couldn’t be with such a huge home/away split. Tiger pitchers finished the regular season with a 3.51 home ERA – good for 5th in the AL – and a .691 home OPS allowed. On the road those numbers rise to 4.05 and .744. That road ERA is still good for 6th in the AL (and still better than the Yankees) – so it looks as though Tiger pitching is less responsible for that big home/away win differential than the offense is. For pitchers we get the opposite split in terms of HR/FB: 11.9% on the road compared to only 9.1% at home with a slight drop in strikeouts and a slight rise in walks – though nothing like the 20% rise in K% for Tiger hitters on the road. If we only looked at Tiger pitchers, we could chalk that home run rate up to the big park – but given that Tiger hitters seem to do so much better at knocking the ball out on Comerica Park I doubt that’s the whole story.
The impression that I’m getting is that not only is the old story of “favorable ball/strike calls for the home team” at work here, but Tiger hitters (and to a lesser degree, pitchers) are unusually dependent upon those calls. It’s awfully hard to get information about batter splits that includes data for something like “strikes looking” – though we have that information for the season overall. For pitchers, on the other hand, that stuff is out there for any who care to look. What we see is that (to use a few examples) Rick Porcello and Justin Verlander get approximately one more called strike (rather than a ball) in each home start than in each road start and also one more swinging strike. That doesn’t sound like much, but if it means as little as one extra out at home that they wouldn’t have gotten on the road that really is enough to drop that ERA by half a run.
We can only assume that Tiger hitters are getting the same benefit and doing some damage in those 2-1 counts that would have been 1-2 on the road. The question remains – WHY do Tiger hitters need those calls more than other hitters?