Being a guy who has almost total faith in numbers leads to some interesting consequences. Last year, after Penny got pounded time and time again, I had complete faith that he would bounce back. While his walk rate had taken a slight jump, his strike out rate had actually improved and his spike in home run rate was simply regression to the mean. Despite my faith, Penny never got better, and I spent the winter concerned that he would be traded for Juan Encarnacion.
Coming into this game, Brad Penny had the second lowest ERA in baseball, yet I'm scared to death whenever he takes the mound. I keep waiting for Penny to strike someone, anyone, out, but it doesn't happen. After tonight's six inning, two strike out performance, Penny's K/9 stands at 3.06, third lowest in the majors, and his strikeout to walk ratio is .84. How did Brad Penny go from being a power pitcher to a guy that simply can't miss bats at this point in the season? If this is permanent, can he keep up his success?
The answer to the "is this sustainable" part is pretty simple: no. Penny cannot be an effective pitcher with his current strikeout and walk rates unless his home run rate stays at zero. Right now, Penny is doing pretty much what Mark Hendrickson did to make himself appealing to the Dodgers: put up an unsustainable line drive rate. Pitchers have very little control over how many line drives they allow. This is the reason why pitcher's BABIP's can fluctuate so wildly from year. Penny's line drive rate is 8.2%, second lowest in the majors. I can guarantee this won't last. While Johan Santana has a similarly low line drive rate, he gets a good percentage of his outs on strikeouts. If Penny's line drive rate regresses to the mean and he continues letting the opponent put balls in play, it could be a very long season.
Not only is Penny avoiding line drives, he's been getting a ton of double plays. Penny has induced a double play 31.3% percent of the time, fifth highest in the majors. While this isn't entirely luck, Penny's ground ball to fly ball ratio of over two to one and lack of strike outs has something to do with it, I have to imagine that this is a stat that will tend to regress to the mean. (I plan on looking in depth into this at a later date.) All I can say is that right now it seems like Penny is able to constantly able to get out of jams with the key double play, and I don't think he can keep this up.
The only part of Penny's current streak he might be able to keep up is his low home run rate. If Penny continues to allow a fly ball less than one fourth of the time, Penny could end up with a Derek Lowe-esque low home run rate. While Penny won't keep up his astronomically low ERA, he could be a semi effective pitcher if he's able to keep the ball in the park.
So, what has changed between this season and last season? I can't say for sure without pitch-by-pitch data from last year, but Gameday's new advanced pitch tracking can give us a few hints. According to the Bill James Handbook, Penny is the hardest throwing starter in the National League. He led the NL in "pitches thrown over 95" by a huge amount. It's safe to say that Penny is the only pitcher in the NL whose fastball sits at 95+. This season has been pretty much the same. In his starts against the Pirates and the Rockies, his fastball was clocking between 94 and 98. Tonight his velocity was slightly down, his fastballs ranged from 92-95, but the results were the same. A lack of velocity is not Penny's issue.
What is notable is how little Penny's fastball moves. While this has been noted by most people who watch the Dodgers frequently, it's kind of scary to see a number attached to it. In the limited time I've been using the new Gameday, I've noticed most pitcher's fastballs break four to five inches. Penny's generally breaks three inches, and sometimes as little as two. However, anecdotal evidence suggests that there's not much different here.
Without the previous years data to compare Penny's starts to I can't say why Penny's strikeout rate has suddenly dropped. All I can say for sure is that he probably isn't hurt, and maybe this is just a sample size issue. That's the best I can hope for.
There is no pitcher in history that has been able to sustain success with a strikeout rate of three per nine and a strikeout to walk ratio under one. Whatever has changed for Brad Penny in the last year needs to get fixed soon, or our dominant pitching staff could start looking mighty shaky.