BP lists the bottom 5 rotations in the AL, by SNLVAR, in order, as the Mariners, Tigers, Rangers, Devil Rays and Royals.
While although I don't truly understand the SNLVAR statistic, I looking around the AL, I find it hard to believe that the Tigers are the second worst rotation. There are plenty of teams that are worse, and the Tigers rotation might have the highest upside in the entire league.
I immediately can think of a couple that are worse: Yankees and Red Sox. I'm taking into consideration park factor and the frequency of facing most of the best hitters in baseball.
The Sox' "rotation" currently consists of Beckett (an NL transfer that has some noticable splits away from Florida), Arroyo (a solid #4), Schilling and his bum ankle, Wells and his bouts with gout, Clement (who pitched like a #4), Wakefield (a solid #2/3) and Papelbon (a rookie). Hmm, looks a little overrated to me.
Yankees. Randy Johnson (didn't pitch like an ace last year, but was still the best pitcher on either staff), Mussina (pitched like a #4), Chacon (results were ok, but K/BB are big reason for worry), Pavano (still can't stay healthy), Wright ('nuff said) and Wang (decent #4 when healthy). Money aside, with that rotation they were still 0.01 points behind Detroit in ERA.
I'd be more excited about Detroit's rotation than either of those. Bonderman has the highest upside of almost any pitcher in the majors, but needs to stay healthy, Maroth is a tough pitcher that has improved almost every stat in the past 3 years (except HR), Robertson took a step back last year, but will get help by being around Rogers, Rogers is a terrific 1st half pitcher and can help mentor the young kids, and Verlander, who might make the #4 spot out of ST.
If anyone can explain the SNLVAR stat, please do. For now, I'm going to say that considering the lineups that each team has to face 18 or 19 times per year, the park and the potential to stay healthy and improve on last season's numbers, I'd take the Tigers and move the Yankees to #2 on the aforementioned Bottom 5 list (behind the Mariners) and the Sox #3.