The Kansas City Royals' starting rotation hasn't missed many bats since Zack Greinke was swapped to the Brewers prior to the 2011 season. In fact, the collective K rate of K.C.'s starters since 2011 (5.97 per nine innings) is the lowest in the American League this side of the ground ball-heavy Indians and the pitching pinata that is the Minnesota Twins' staff. But Danny Duffy is out to change that woeful whiff ranking.
While the 23-year-old lefty's control still needs plenty of work (he walked 4.4 batters per nine frames as a rookie in 2011, and 4.8 per nine so far in 2012), Duffy is punching out hitters at an elite clip. He has struck out 10.3 hitters per nine in 2012, the fourth-highest rate among starters throwing at least 20 innings and a big jump from last year's 7.4 K/9. Duffy's extra Ks come from a souped-up fastball and a change in curveball location that's leading to lots of awkward swings.
Duffy threw plenty hard as a rookie in 2011 (he averaged 93 mph with his fastball and topped out at 98.2 mph), but he has found even more giddy-up on the pitch this year. He is averaging 95.1 mph with his fastball and has gone as high as 99.5 mph on the radar gun. No starter this side of Stephen Strasburg brings that kind of heat:
Highest fastball velocity among starting pitchers, 2012
Opponents have whiffed 21.6% of the time that they have swung at Duffy's fastball this year, up from 18.9% in 2011. Duffy's fastball miss rate places him in the top ten among starters:
Duffy's fastball is vital to his success, as he's throwing the pitch two-thirds of the time and has used it to record 15 of his 26 K's. But by adding some zip to his curveball and deploying it as a chase pitch, Duffy is getting many more swings and misses with his breaking stuff as well.
His curve has also added a few ticks of velocity (from an average of 75.6 mph in 2011 to 77.2 in 2012). As a rookie, Duffy threw about 50% of his curves in the strike zone. This year, he's throwing 41% of them in the zone. His chase rate with the pitch has spiked. First, take a look at hitters' swing rate by pitch location against Duffy's curve last season, and then the league average for starters:
Though Duffy got some lefties to go after curves tossed low-and-away, his overall chase rate with the pitch (21%) was well below the American League average for starters (27%). In 2012, however, he's getting many more chases:
Duffy's chase rate with the curveball has improved to a healthy 32%. Right-handed hitters are especially jumpy, going after 44% of curves thrown out of the zone. Those extra cuts on out-of-zone curves are resulting in more whiffs: Duffy's miss rate with this curve has climbed from 22% as a rookie to 34% in 2012 (the average for AL starters is about 26%).
Back as a prospect in 2010, Duffy actually briefly called it a career during spring training. But he missed the game and, seeing as he's left-handed and throws harder than nearly anyone on the planet, the Royals gladly welcomed him back. It's too early to tell whether Duffy is headed for Greinke-like acedom or perennial disappointment due to shaky control (see Sanchez, Jonathan), but his power fastball/curve combo is doing a fine job of making hitters contemplate their own retirement right now.