There are few things star players can't do. They can even swing the fate of the World Series in one direction or the other.
For example, the Arizona Diamondbacks would not have won the World Series in 2001 without Curt Schilling and Randy Johnson, and the Florida Marlins probably would not have won the 2003 World Series without Josh Beckett.
However, the World Series can also be determined by players who weren't supposed to make much of a difference. David Freese in the 2011 World Series comes to mind, as do Edgar Renteria in the 2010 World Series and David Eckstein in the 2006 World Series.
So while you're keeping an eye on stars like Miguel Cabrera, Prince Fielder and Buster Posey in this year's World Series between the Detroit Tigers and the San Francisco Giants, you may want to watch out for the X-Factors as well.
If we define "X-Factors" to mean players who could either make a major difference or no difference at all, then there are five players on each team you should be looking out for in the Fall Classic.
And they are...
Note: Stats courtesy of Baseball-Reference.com unless otherwise noted.