To be fair, I'm not a Tiger fan. I'm a Cub fan. But, through a very complex, yet quantifiable, system of rooting I can become emotionally invested in the Tigers. To wit:
The Chicago Cubs trump all. That's my team and I live and die by every pitch.
The Cubs play in the National League which is distinct from the American League because of the Designated Hitter. The "DH" is an aberration of human evolution. It means that the pitcher doesn't have to hit. In real baseball, i.e., the National League, the pitcher has to hit.
Now, there are 2 seperate baseball Leagues---the Al, and the NL. In each League, the teams are split by 3 "divisions." The Eastern, Central, and Western.
In the NL Central, we have the Cubs, the Cardinals, the Rockets, and the Brewers. Since the Cubs suck and the Cards are good, a Cub fan roots against the Cards every chance we get. Division-wise, the Cardinals are the team that have kept the Cubs out of the playoffs more than any other. So, Cubs fans hate the Cards. If any team plays the Cardinals, us Cub fans root for the team that is playing the Cards. Unless.....
The Cardinals were to play the Chicago White Sox. The White Sox are the AL team in Chicago and they, of course, play with a Designated Hiitter. Since rooting for the NL trumps rooting for the AL, but rooting for the weaker team in Chicago trumps all, I would root for the Cardinals against the White Sox.
When the Cardinals play against any other AL team, I would root for the Cardinals because the NL is the better brand of baseball.
But, in the case of St. Louis vs. Detroit, I root for Detroit because that was my hometown team. Hometown team trumps anger against the DH unless you're favorite NL team has nothing against the NL team playing in the Series. In other words, if the NL team playing my hometown team were an NL team other than the Cardinals, I'd root for the NL team. But since the NL team is the Cardinals, who has kept my Cubs from success, coupled with the fact that my hometown team was the Tigers who are now playing the Cardinals--------well, I can now root for the Tigers and my hippocampus is good.
If you don't understand that, than you don't know baseball.