Disclaimer: This post is not intended to inspire or promote gambling.
With that said, I'll restate the title: Are the Tigers undervalued at 8/1 odds to win the World Series?
Yes, the rotation has been altered given the (atrocious) Doug Fister trade. But, is inserting (the very capable) Drew Smyly really that much of a downgrade? Buster Olney doesn't think so. He still rates the Tigers rotation as the best in baseball.
In addition, it is no secret that the Tigers defense and speed will be significantly improved from a year ago. Castellanos and Iglesias offer significant improvements in the field over Cabrera and Peralta. In addition, Rajai Davis has an opportunity to be a true weapon on the basepaths.
The bullpen is still a question mark. Contrary to popular belief, it wasn't truly terrible last year (13th in FIP last year at 3.61). However, if you figure in the gap between ERA and FIP (i.e. underperforming your peripherals, which is largely a product of the environement you play in and the defense behind you), only 2 teams underperformed more than the Tigers: The Rockies (makes sense) and the Mariners (not so much). Yet, regardless of how memorable bullpen losses can be, the bullpen makes up such a small component of the team when compared to the offense, the defense, and the starting pitching. Roughly speaking, the average team produced 19 WAR from position players, 11 WAR from starting pitchers, and 3 WAR from the bullpen. Even if the bullpen is 30% worse, it may only mean 1-2 wins over the course of a season. For a reference point, the Tigers were above average in all three categories a year ago, measuring 26.5, 25.3, and 4.1 WAR, respectively.
In addition, the Tigers play in the easiest division in the American League. A division crown creates an inside track to the World Series, having to only win 3 series to win the title. If all teams are equal, that gives each team who makes the ALDS a 12.5% chance of returning champions. Sure, people can argue that they only finished a game ahead of Cleveland for the AL Central crown, but it wasn't as close as you think. According to Pythagorean predictions, the Tigers should have won 100 games based off of their run differential (+172) and the Indians should have won 91 (+83). That speaks to the little bit of "good luck" the Indians received and the healthy serving of "bad luck" the Tigers got on the other end.
Entering the season last year, the Tigers were at 7/1 odds to win the World Series. As of a few weeks ago, they were posted at 8/1. At other online sportsbooks, those odds are as high as 17/2. Why so high? At those odds, mathematics predict that the Tigers will win the World Series 11.7% of the time. With the vig going (usually 10%), oddsmakers would predict that the Tigers would win the world series less than 10.7% of the time.
I just find it hard to believe that the Tigers are significantly worse than they were a year ago. They should still win the AL central (should being the key indicator), and will be able to compete with the other contending teams in the American League. Of course, there are key injuries and suprises in every MLB season. But, there is a reason that the Atlanta Braves won 14 straight division titles (1991-2005) and the Yankees went to the playoffs in 17 out of 18 years (1995-2012). Competitive baseball teams in the modern era tend to stay competitive. I believe this to be true in the Tigers case, especially when Dombrowski continues to make savvy moves (Fister trade excluded).