Wuertz's slider has been the toughest pitch to hit in all of baseball this season.
The pitch has a 49.7 percent swing-and-miss rate, narrowly ahead of Royals starter Zack Greinke's slider (49.0 percent) for tops in the Major Leagues, according to baseball analyst Harry Pavlidis in a July 15 report in the Wall Street Journal.
The Cubs' Rich Harden's changeup (48.6 percent), the Yankees' A.J. Burnett's curveball (48.3 percent) and the Rockies' Jorge De La Rosa's slider (42.5 percent) round out the top five.