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You see a lot of new fangled baseball statistics with strange acronyms but Occam's Razor rules here in Baseball by the Numbers. The simplest stats that work are deemed best. So let's go old school like we used to when we were kids and flipped over the baseball cards to see how many batters pitchers punch out and walk.
The K:BB ratio is our focus today. The line of demarcation separating the dominant enough from the dominant challenged is two Ks for every walk. Through Memorial Day, 52 pitchers met our threshold. The eligibility requirement is one inning for each game, so relievers are out (we don't have nearly enough data yet to fairly evaluate them).
Most of these guys are really good and thus highly valued. That's what we'd expect if the stat has merit. But there are some who have relatively low perceived value who not only are on the list, but high on it. And, similarly, some pitchers who are perceived to be very solid struggle in K:BB ratio and thus, according to this metric, are poor bets to continue their current level of success.
As a check, we also look at a pitcher's fielding independent (FIP) ERA. So we recommend a pitcher with a plus-2 K:BB only when his FIP ERA is under 4.00. And we do not downgrade a pitcher unless his K:BB ratio is less than 2.00 and his FIP ERA is over 4.50. We pay no attention to his actual ERA because we're only interested in how pitchers will perform from this day forward.
Remember, we're trying to beat the market by targeting guys it will value too low or too high because of their narrow obsession with ERA.
The league leader in this stat is not Zack Greinke(notes) or Johan Santana(notes) (who are both very good at fourth and fifth best, respectively). The Twins' Kevin Slowey(notes) has 9.75 Ks for every walk due mostly to the microscopic 0.65 walks per nine innings. Slowey is generally undervalued and should have an ERA of 3.97 even with all the gopher balls. His WHIP of 1.39 also should be expected decline to a level much closer to 1.00 for the balance of the year as long as his walk rate remains near 1.00 per nine innings.
Other guys who meet our "Buy" criteria while being undervalued by the market either for present ERA or past performance are Carl Pavano(notes) (3.64 K:BB, 3.73 FIP ERA), Koji Uehara(notes) (3.45, 3.87), Joel Pineiro(notes) (3.14, 3.27), Wandy Rodriguez(notes) (3.11, 2.56), Edwin Jackson(notes) (3.00, 3.46), Randy Wolf(notes) (2.63, 3.94), Zach Duke(notes) (2.60, 3.56) and Gil Meche(notes) (2.05, 3.01).
Guys overvalued by the market relative to their K:BB and FIP ERA (and thus all "Sells") are Rick Porcello(notes) (1.97, 4.71), A.J. Burnett(notes) (1.85, 5.29), Joe Saunders(notes) (1.81, 4.68), Edinson Volquez(notes) (1.45, 5.15), John Maine(notes) (1.20, 4.65), Tim Wakefield(notes) (1.22, 4.95) and Mike Pelfrey(notes) (0.94, 4.74). Pelfrey is 97th among the 99 qualifying starters in K:BB.
Now let's look at these and others who just missed the cut in more detail.
Kyle Lohse(notes), Cardinals: His FIP ERA is 4.01. But that's close enough for us. The 2.38 K:BB is comfortably good. For 2008, Lohse had a 2.43 K:BB and a 3.89 FIP. And the K rate is now a useful 6.29/9.
Justin Masterson(notes), Red Sox: He just misses the innings cut, but his 4.47 actual ERA is likely a fluke given his 2.53 K:BB and his 3.63 FIP ERA. The risk is that his low homer rate of 0.61 per nine innings is lucky low; FIP doesn't account for that. Still, the other indicators are too good. Masterson is at least a solid No. 5 fantasy starter in all formats if he gets another crack and odds are great another Red Sox starter will get injured or demoted.
Wandy Rodriguez, Astros: He's coming off a Memorial Day start where he was hit uncharacteristically hard. I'll settle for the smallest of discounts. Rodriguez has many skeptics, still, for reasons I do not understand. These skeptics likely do not include his present owners, but it doesn't hurt to ask.
Zach Duke, Pirates: I never liked him, but when the facts change, I change my mind. As British economist John Maynard Keynes once asked, "What do you do?" The K-rate was the big problem for me at 3.44 and 5.4/9 in 2007 and 2008. This year, though, it's 5.40 (acceptable) and his walk rate is currently a career best.
Koji Uehara, Orioles: I like the peripherals, but his hamstring injury still might force him to the DL or prove to be a nuisance for the next two or three weeks. So hold off on grabbing him for now.
Matt Cain(notes), Giants: I'll change my mind about Cain when the data changes. But right now, he's 73rd in K:BB between Braden Looper(notes) and Brian Tallet(notes) and his FIP ERA is 4.36. And I can't assume low HR rates for extreme fly ball pitchers like Cain no matter how big their home park.