The Exception to the Rule: How to Profit in Fantasy Sportsdiscounting all pitchers, you might buy the exceptional ones at a significant profit.
If everyone believes pitchers with low BABIPs in a given year will regress to roughly the league average (or at least the average given their teams' parks and defense), and you've noticed Mariano Rivera has a career BABIP well below it, you'll realize projections systems which normalize for BABIP will undervalue him.
Certain players and classes of players are exceptions - for some particular reason or collection of reasons they don't adhere to the general truisms which form the basis of most projections systems.
Discerning which players aren't subject to the normal rules isn't always easy. Heading into 2013 one might have thought Matt Cain had a Rivera-esque quality in preventing hard contact, proving to be incredibly stingy in BABIP and HR/FB allowed. But while the BABIP trend persisted last year, the HR rate spiked, and that was without Cain giving up significantly more fly balls. While Cain's K:BB and K:9 numbers have always been good, but not great, prior to last year he had out-pitched those peripherals just as Rivera had. Going forward, however, is 2013's 1.12 HR/9 the new baseline? And given he had that rate in a pitcher-friendly home park, do we have to re-think whether he retains the ability to induce weak contact? In other words, is Cain still an exception to the usual metrics we apply?*
By contrast pitchers like Ricky Nolasco and Joe Blanton seem to get hit especially hard. Nolasco's career ERA is 4.37, but his career FIP is 3.80. For any one year, you might think that disparity portended an ERA correction in the direction of his FIP. But Nolasco consistently under-performed his K:BB and K:9 rates - likely making him an outlier. (And Blanton makes Nolasco look like Cain or Rivera).
Marco Estrada's another interesting pitcher. Over the last two seasons he's had 261 Ks and 58 walks in 266 IP - numbers that look like a full season of Justin Verlander. But Estrada's a fly ball pitcher in a decent home run park - he gave up 37 HR over that span. As a result, while his WHIP is likely to help you a good deal, his ERA is roughly the NL's league average. While some people expect Estrada to take a leap given his strong K:BB and K:9 numbers, those come in part as a result of his putting the ball over the plate - the same tendency that results in the homers. This is an instance where the normal indicators could be misleading.
In any event, I've delved into some specific examples, but the larger point is more interesting to me: that with good information being so readily accessible even to casual fantasy owners, the easiest way to profit is to look for a general rule that informs player valuation and find exceptions to it.
* I'd say yes given his low BABIP, the small sample of HR/FB for one season and no loss in velocity.