As we enter the last few weeks of the season, the basic contours of the pennant race are nearly set in stone. With time running out, if you're not in the playoff picture at this point, it's quite unlikely that you'll be in the playoff picture again until 2013. We've blown past the deadlines for non-waiver trades and for getting a player onto the postseason roster, so not only have the potential acquisitions declined in quality, but teams can no longer bring in anybody new for October. That creates a new series of challenges for teams currently fighting it out for the postseason, with the focus for September roster improvements mostly coming from internal options rather than the wheeling and dealing you see in July.
Through Sept. 3, 2011, the Boston Red Sox stood at 84-54 (a .609 winning percentage) and held a nine-game wild-card lead over the Tampa Bay Rays. Unless you spent the past year stranded on a desert island, busy fashioning a raft out of branches and homemade rope in order to get yourself back to civilization, you probably noticed that Boston's status at the end of September was considerably less rosy than it was at the start of the month. While much was made of the situation in the clubhouse after the collapse, the Red Sox rotation was also a mess for most of the month and there was no good way to fix it at that point. I think I'd want a stiff drink in the dugout as well if I was watching John Lackey, Tim Wakefield, Andrew Miller, and Kyle Weiland getting a lot of starts in a pennant race.
Collapsing as badly as the Red Sox did is an extremely unlikely scenario for any team, but teams with depth concerns and not a whole lot in the way of reinforcements -- even good teams -- have the potential to collapse. So, which playoff teams have the biggest potential for a lousy September that kills their playoff chances?
To answer this question, I asked the ZiPS projection system and a Monte Carlo simulator to play the last month of the season a million times and to report back the 10th percentile performances, meaning the final months so bad that a team has a 10 percent chance of achieving it, and to see which teams came out the worst. In the end, the Yankees, White Sox and Braves came out on the bottom. A simulation's fine and dandy, but these teams all have significant real-life concerns that could make clunkers out of their Septembers.