Unless you're an extreme ground ball pitcher, it's very difficult to pitch in Yankee Stadium without strikeouts. Any team would love to have a pitcher that can put up a 20+ K%, but for a team that plays in one of the most hitter friendly stadiums in the game, a high K% is a near necessity.
After watching his last couple of starts, I've started thinking about my perception of David Phelps a year ago. Back then, the starter was lumped together with fellow B/C grade pitching prospects Adam Warren and D.J. Mitchell. None of these guys could be considered strikeout pitchers, but they all posted solid rates and ERA's in a somewhat pitcher friendly International League in 2011. Perhaps in a different system, these prospects would have gotten more received more hype, but in a notoriously pitching oriented minor league organization like the Yankees, and already approaching their mid-20's, no one expected any of the three to be more than a back end starter.
Now, this season, Mitchell has moved on from the Mariners, after being traded there for Ichiro Suzuki, and he's currently with the Mets, struggling to pitch in the PCL. Adam Warren has found himself a spot on the Yankees' major league roster as a long man, and his velocity has gained a few ticks while working out of the bullpen. The right-hander is currently posting a 3.12 ERA and a 3.87 FIP in 34.2 innings, while maintaining an 18.9 K% and a 6.3 BB%. As solid as he's been, the peripheral stats aren't far off from what we saw in the minor leagues. After posting a 7.1 K/9 through 497.0 innings in the Yankee minor league system, it's not hard to imagine that he'll continue his current 7.0 K/9 he's shown in 2013. His evolution in the bullpen role has shocked many, but David Phelps' transformation has not only been more dramatic, but it's growing more and more believable.
In 2011, David Phelps put up a 3.19 ERA and a 3.69 FIP, along with a 20.0 K% and a 5.8 BB% in Triple-A. 2012 was his first season in the majors, and through 99.2 innings between the bullpen and the rotation, the right-hander not only maintained the low-3 ERA he had in the minors (3.34), he increased his K% to 23.2. During the offseason, there were tons of discussions by fans about what his actual trade value was. Though the pitcher had posted a strong ERA and K rates, his walk rates weren't thrilling, his LOB% and HR/FB rates were too high, and his FIP was a very average 4.32. There were other concerns as well, his high K% was not a product of good breaking or offspeed pitches, and his 7.1 SwStr% would have placed him around the 13th lowest if he'd met the qualifying innings mark. His other contact and swing rates suggested that perhaps some of his achievements were due to hitters swinging at bad pitches outside of the zone, but there was still little reason to believe that his K% would continue at such a high rate with so few whiffs.
Through 68.1 more innings, Phelps is now approaching a major league sample size equivalent to a full season. In 2013, he's lowered his home run rates, his LOB% has regressed to a more appropriate number, and his BABIP hasn't looked as clean, but everything else has sustained. Though his ERA is up to 4.08, FIP is down to 3.56, and he's posting batted ball rates nearly identical to last year. His BB% has increased just slightly to 10.1%, but his K% has remained a 22.7%. That K% was supposed to regress, and even with his continued strikeout success, Phelps is still posting a 7.0 SwStr% in 2013. It's hard to fall in love with this sort of strikeout production, but it's certainly gotten the job done. Phelps has lived on called strike threes.
Even with the sample size growing and his production continuing, I'm wary that hitters will adjust to his style of pitching. In the past, living on the corners is a good way to generate poorly hit batted balls, but perhaps in today's game, which now concentrates on walks, living on the corners is a good way to generate strikeouts as well. Overall in baseball, strikeouts seem to have increased along with walks, and that's a product of players and coaches putting an emphasis on sabermetrics. Phelps' BB% isn't too inspiring, but he's already shown excellent command of the strike zone in the minor leagues. I'd theorize that its that same command, the same style of living on the corners of the strike zone, that's helped him generate high K% and high BB% at the major league level.
Players that were once swinging and making contact with everything are now taking these close pitches and attempting to draw more walks. While Phelps' style of generating strikeouts is not traditional, I'm starting to believe that it's sustainable. The team's decision to send down Ivan Nova, who owns much better swing and miss stuff, and keep Phelps in the major leagues may also be an indication that they also believe he can continue his success.