A good barometer for mixed leagues is that all pitchers with a better than 3-to-1 strikeout-to-walk ratio should be owned. Usually, that gets you very workable averages in WHIP and ERA. (For "only" leagues, the barometer is lower – 2/1.)
Usually is the operative word though, as it usually is in this space. Of course, there are exceptions to the rule. But if you buy the rule, you really need to be willing to buy the exceptions. And the best thing is, they are cheap (or at least cheaper than they should be).
It's a very good bet that if the K/BB ratios of the following pitchers stay close to their rate thus far in 2012, their ERAs and/or WHIPS will get much better. For a sense of how much better, consider that thus far in 2012, the ERA of all starting pitchers who have a K/BB ratio of better than 3.0 is 2.94 and average WHIP is 1.08. Even if the following qualifying starters with a K/BB of 3.0 or better with an ERA of 4.00 or worse (through Wednesday) get only halfway there going forward, they will be assets:
Pavano is one of the strangest pitchers in major league history with a 2.56 career K/BB ratio with a 4.35 career ERA. That's the third worst ERA ever for any pitcher better than 2.5, tied with Kevin Tapani after rounding and behind David Bush's 4.70. Yes, I have been burned by all of these guys in the past due to this rule, which generally has served me quite well (as it will you). But I've always liked Chris Capuano because of it and look how that's worked out thus far this year. The key is that these guys are never expensive, so you have little to lose.
Nova is funny because he's gone from sabermetric outcast to darling in one year while his ERA has moved in the wrong direction. See what you get when you improve your K-rate dramatically? It makes no sense that when you nearly double your K/9, your ERA nearly doubles, too. Especially when your walk rate is lower. Plus the Yankees are going to start hitting so the wins will be there. So I'd grab Nova now, considering he's on the waiver wire in most leagues.
Gee is similar in a lot of ways and has the advantage of pitching in an especially weak-hitting NL this year. Ian Kennedy and Dan Haren will at least be cheaper to trade for and you probably will be getting an elite starter going forward. Hughes was a former top prospect and the last time his K/BB was nearly this good was in 2009 when his ERA was 3.03 and WHIP 1.12 (though that was mostly in relief). With Arrieta , the problem is homers – nine allowed in just 61 innings. But there's a good chance that rate improves, perhaps significantly. Chen in deeper formats has been solid/average now for three seasons.
Scherzer deserves a graph of his own. In two starts, he's been 26/2 in K/BB. In the others, 37/17 - still good but not nearly as bettable. All this is moot in most leagues, as Scherzer, given his 15-K game on May 20 against the Pirates, makes him too expensive. Note, too, that R.A. Dickey got 11 whiffs in seven innings against the Pirates soon after Scherzer's outing (and I like Dickey in -only leagues, but he's not a big strikeout guy by any measure).
Now is time to upset owners of the following pitchers by noting that they are likely very lucky in posting at least ERAs far better than their K/BB suggests. All these guys are under 2.0 in K/BB. The averages for all starting pitchers with a K/BB under 2.0 this year are 4.22 ERA and 1.37 WHIP. These are the only pitchers with a K/BB under 2.0 and an ERA lower than 3.50, though their WHIP is noted, too.
These guys are all sells, especially Darvish. Again, as I say all the time, "sell" often means "trade." If Darvish's perceived value is higher than his expected future value, you win the trade unless you are a terrible negotiator. So go out there, Darvish owners, and win one.
Volquez's problem like Darvish's is walks. They're basically the same pitcher, though Volquez has much less perceived value. Alvarez can't strike out batters and thus is worthless in most Yahoo! formats. Lilly also isn't striking out batters, so is a tough sell. With him, I'd have my finger on the trigger to reserve or release at the first sign of the correction that's certainly coming (especially in WHIP). But no need to go into details when everyone on this list is likely to regress in at least one key category. If you keep them, you must argue that their K/BB will improve. If you do, make sure you are not wishcasting. I think we have enough season now where what you see in K/BB is generally what you will continue to get.