I've blogged before about the similarities between the 2005-06 White Sox and the 2006-07 Tigers. Both teams won the AL pennant with a fluky good pitching staff, low team OBP, and decent power. The next year, both teams got fluky good seasons from a few hitters to balance the pitching regression, although they still missed the playoffs.
In 2007, the White Sox offense crashed, going from a 103 OPS+ to 87. People who don't believe in computer projections think that Chicago's 72-90 record wasn't representative of the team's real talent, and they're right: their Pythagorean record was 67-95.
Will the 2008 Tigers suffer a similar fate? I don't think they'll lose 90 games, but they should feel some serious decline. The Tigers figure to get substantially worse at three offensive positions just by regression to the mean: Placido Polanco, Curtis Granderson, and Magglio Ordonez all gained 140 or more points of OPS from 2006 to 2007. That sort of sudden growth doesn't stick, especially when it's heavily driven by batting average spikes.
Much was made of the Tigers' trade to pick up Edgar Renteria, but his 2007 was another batting average-driven mirage, and he's not really a much better hitter than Sean Casey, the man he's replacing in the lineup. Detroit will get more offense out of the first baseman next year, but the loss at shortstop should balance it out.
The Tigers, much like the White Sox, have an old everyday lineup--only Granderson is under 31--and it's easy to underestimate how much total decline a team will suffer when its entire batting order is past their prime.
Detroit does have one player who figures to improve substantially, assuming he is healthy: Jeremy Bonderman is much better than last 2007's 5.01 ERA would indicate. But he can't single-handedly rescue a pitching staff that has one of MLB's worst bullpens and only one other above-average starter (Justin Verlander).
If you want your co-workers to think you're a genius, tell them that in 2008 the (Devil) Rays will win more games than the Tigers. There's probably about a 50% chance it'll happen, and everyone will think you're the second coming of Nostradamus.