When thinking about strikeouts, what usually comes to mind is a pitcher blowing away a hitter with high-90s heat. However, in a season in which strikeouts have been rising, pitchers have thrown fewer fastballs with two strikes in 2011 than they had through this point in 2010.
As a result, pitchers are recording a higher percentage of strikeouts using offspeed pitches.
Felix Hernandez, second in the American League with 134 strikeouts, has seen his changeup become his most effective two-strike pitch. In fact, with two strikes in the count, out of the 97 plate appearances that ended in a changeup being thrown, Hernandez recorded 58 strikeouts, the highest strikeout percentage using the changeup for any starter in the majors.
When using his fastball in those same situations, of the 108 plate appearances, only 38 resulted in strikeouts, a drop-off of more than 20 percent.
Highest K Percentage
Two-Strike Count Using Changeup
Not far behind Hernandez is James Shields, whose changeup has led to a great first half for the Rays ace. He has recorded 73 strikeouts with the changeup, the most by any pitcher so far this season. Batters are hitting only .103 off Shields' changeup with two strikes in the count, and nearly 56 percent of those plate appearances that have ended in a changeup resulted in strikeouts.
Justin Verlander, tied for the major league lead, is armed with a deadly fastball, but has also used his changeup effectively to close hitters out.
Overall, batters have been hitting .212 off his changeup. But when he throws it in a two-strike count, that number drops to a .058 average. Verlander ranks fifth in strikeout percentage when throwing the changeup with two strikes.
While the changeup has been the key strikeout pitch for some notable pitchers, it's actually the slider that has experienced the largest bump -- nearly 20 percent of Ks in 2011 versus 19 percent in 2010 -- and is a pitch many premier strikeout pitchers have relied upon this season.
Most Strikeouts Using Slider 2011
No pitcher has used the slider more effectively than Clayton Kershaw, who is currently tied with Verlander for the league lead in strikeouts. Kershaw leads all pitchers with 75 strikeouts via the slider.
CC Sabathia is tied for third with 64 strikeouts using the slider. Nine of his 11 strikeouts in Tuesday's victory over the Cleveland Indians came on that pitch.
Successful relievers have also leaned on the slider in 2011, with no one being more effective than Jonny Venters. In two-strike counts, out of 41 plate appearances against Venters that ended with a slider, 37 resulted in strikeouts. In those same plate appearances, he has allowed only one hit.
Amazingly, his putaway rate, a metric diving number of strikeouts by number of pitches thrown, is 43.5 percent when he throws a slider with two strikes in the count. That's extremely efficient considering the major-league average for putaway rate on all two-strike pitches is only 17.5 percent.
-- Jason Starrett contributed to this report