There are more than a few fantasy owners unhappy with Dan Haren right now. Sure, he's picking up plenty of strikeouts, and thankfully, he's keeping his walks down as he always has, but he's killing you in a few categories relative to where it is you drafted him (or how much you paid for him at auction). The big question is whether or not you should be concerned about him going forward, and what it is you should do if presented with a trade offer from someone more optimistic than you.
Eric Seidman and Matt Swartz listed Haren as someone you should expect to rebound based on his SIERA—there's reason to believe that, but just for the sake of playing devil's advocate, let's look at a situation in which Haren may not return to form. Over his last 26 starts, dating back to July 23, Dan Haren has been kind of a mixed bag:
The strikeout rate is excellent—he's actually been better than that in his 82 innings this year, at 9.1 per nine. The home run rate is a combination of second-half struggles in 2009 (1.3 per nine) and a poor start to this year (1.8 per nine)—you can say that he's given up some extra bombs this season and that his homer rate will stabilize with some additional innings, but there's a chance he goes right back to that 1.3 rate rather than his stellar first half success from 2009.
Haren is normally solid at keeping the ball in the park and occasionally has his years where he puts the ball on the ground more often, but he's generally posting average G/F ratios. This year the F portion of that ratio has flown out of the ballpark 17 percent of the time—that's high, but he was at nearly 12 percent last year and has been as high as 13, making it not so outrageous either.
In summary, here's what the take on Haren has been: he's going through a rough stretch and should recover by giving up fewer homers than he has been. Then the strikeouts and walks will allow Haren's ERA to move closer to his SIERA. The possibility exists though that Haren is not just going through a bit of a rough stretch—the strikeouts and the walk rate are there, but the ball has been flying out of the park for more than just two months. Arizona's defense—which is called thus solely because they wear gloves and are expected to field balls in play, not because they actually succeed at doing so—has been a huge impediment to Haren's success as well.
While it's great to know Haren has been unlucky in that regard, it's not like Arizona is going to bring in a new defensive unit anytime soon. You're stuck with them just as much as Haren is if you drafted him. Haren hasn't helped himself with the home runs, but a significant portion of the blame for his .279/.316/.485 line allowed over his last 26 starts can also be placed on that D.
Which brings me to the last knock on Haren in 2010: he's typically a first-half success and second-half disappointment. From 2007-2009, Haren has posted an ERA of 4.33 in the second half, while keeping his cumulative ERA from those three years at 2.34 pre-All Star break. That’s a huge difference, and we're talking about inning samples of 385 for the first half and 283 for the second half—sure, you would love more to work with, but it's not available, as is often the case when it comes to fantasy analysis.
If he's pitching this poorly now and typically slows down in the second half—well, I'm not suggesting that he'll add another two runs to his ERA and pitch below replacement level, but he may give back whatever he gets back from the home run regression if his strikeouts and walks go in the wrong directions as they have in the past—things may not get any better.
SIERA may be onto something with Haren—we trust run estimators for a reason, you know. The possibility also exists that 2010 is just not a very Haren-like year for the hurler though, and in single-season leagues, you may want to use his excellent K and BB rates as ammunition while negotiating a trade. Do not sell low on him, but if you can get fair value for him, this may be the year to pull off a risky move.