Should buyers beware of Ryan Dempster?

Will Ryan Dempster disappoint the team that trades for him? (Getty Images)

It's easy to understand why the name of Cubs right-hander Ryan Dempster is being bandied about leading up to the July 31 non-waiver trade deadline. First (and most essentially), he's available. Second, he's owed merely the balance of his $14-million contract for 2012. And, third, he's a veteran who's having an outstanding season (his 1.86 ERA leads the majors).

If a team is ogling Dempster because they want to upgrade the middle of the rotation or add depth, then pursuing him is a sensible goal. If, however, they're seeing that sparkling ERA and thinking they're adding an ace, then they're likely to be disappointed.

That's because Dempster's success in 2012 is largely built on a shaky foundation. Yes, he's shown better control thus far, but his strikeout rate dropped to its lowest mark since 2003. As well -- and most critically -- Dempster is likely to regress in some key areas. Specifically, his batting average on balls in play (BABIP), strand rate (LOB%) and home-run/fly-ball percentage (HR/FB) are checking in at levels that almost certainly can't be sustained.

BABIP is the average allowed on fair balls that don't leave the park, and pitchers typically settle into the .290-.300 range. Anything far below or above that span should be considered likely to undergo a correction. As for LOB%, which is the percentage of base-runners a pitcher prevents from scoring, it's usually around 72% for all pitchers, and any deviation from that figure is likely due to luck, bad or good. HR/FB, meanwhile, is likely out of whack when it wanders too far from the 9-10% territory.

With all that in mind, let's take a look at how Dempster this season is faring in those areas relative to his established norms (numbers courtesy of the most-excellent FanGraphs) ...

Dempster, 2012 .242 85.5 6.7
Dempster, career .301 72.2 10.2

Across the board, Dempster seems to be the beneficiary of simple good fortune. He's not, at age 35, a suddenly different pitcher. Take those numbers into account along with the fact that Dempster is giving up more fly balls than he usually does and that his velocity is down a bit, and you have a performance that looks, walks and quacks like a fluke. Regress his BABIP, LOB% and HR/FB, and Dempster's ERA should be 3.71. That's the pitcher teams will be targeting, not the one with the 1.86 mark.

So long as potential trading partners realize that Dempster should be valuated as a good-not-great starting pitcher, he's probably a useful addition. If too much emphasis is placed on his 2012 success, however, the risk of overpay -- and unrealistic expectations -- is too great.

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CBS Sports Writer

Dayn Perry has been a baseball writer for CBS Sports since early 2012. Prior to that, he wrote for and He's the author of three books, the most recent being Reggie Jackson: The... Full Bio

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