What’s Wrong With Ryan Dempster?

Chicago Cubs’ pitcher Ryan Dempster might have thrown seven innings of one-run baseball last night, but some uncomfortable questions still linger for the former 17-game winner and staff ace.

With his latest outing — his first quality start this season — Dempster has an unimpressive 8.05 ERA and 1-3 record. These being the end-all statistics for most Cubs fans, it’s easy for Cubs fans to see what’s wrong with Dempster: He’s terrible.

Kidding. In truth, a little investa-magation helps us understand what’s really happening to the Cubs’ resident jokester.

This year, Dempster has been using his four-seem fastball (think: fast and straight) less often and his two-seamer (think: a little bendy but also fast) much more. The effect has been, eh… kinda the same.

But his main pitch, the slider that’s been his bread-n-buttah in the past four seasons, has been less effective. He’s throwing it a ton (~34%) — more than any other pitch, in fact — but so far gotten some poor results (5.7 runs below average). A look at his Pitch F/x data informs us that his slider, if anything, is sliding even more than last season (which, I;m incline to think, should be a good thing).

So, then, what ails Mr. Dempster? Frankly, the answers are easy: Ol’ fashioned bad luck. Yeah, this “What’s Wrong With [player x]” series often reduces down to this same assertion, but it’s for good reason. We humans are fickle creatures,  prone to emotional reaction and quick frustration. We’re ready to call a player kaput after 60 plate appearances, when in fact flukes and bad luck can extend 10-times that length.

Consider the Great Roberto Clemente. In 1962, Clemente hit a mere 10 home runs and was about 12% above league average with the bat (according to wRC+), despite his career average of 29% above the ruffians. If a Hall-o-Famer can dip 17% from his norm while in his prime, then a great or good or terrible player can do the same — or even more.

But I digress. Returning to Dempster, we find him a ship tossed in the maelstrom of bad luck. CHARTS!

With the exception of his 54 innings in 1998, Dempster has never had a BABIP so high as this season’s (.336). Batting average on balls in play (or BABIP) is a pretty solid estimator of luck. Like with anything, there are lots of wrinkles and exceptions, but being .032 ticks above your career norm (.302) is clearly unlucky.

And before you tarts say, “Oh, it’s just the Cubs ter’ble defense, poo-poo-poo!” please know the Cubs own the third lowest BABIP among NL teams since 2008. (I know, right?)

Again, we see Dempster hitting a career-worst on yet another luck metric. Left on base percentage (LOB%) typically hovers around 72% (for Demp, his career LOB% is 71.7%). This year, he’s sportin’ a 58.8%. That’s a straight kick in the groin from Ms. Luck.

Home runs per nine innings (HR/9) is not a luck metric, but I’m using it as a proxy for HR/FB (we do not yet have a HR/FB graph). Home runs per fly ball (HR/FB) is another — though hotly contested — metric for luck. We can see from the above chart that Dempster has gone all Bill Murray from Stripes on HR/9, taking the metric for a cruise through the German mountainsides.

Despite his a normal career HR/FB (at 10.8%, he’s pretty much textbook), this year he’s allowed 22.5% of fly balls to land in the hands of some bleacher bum. Detractors will say, “He’s just getting hit harder,” and, “Raising Hope isn’t that funny,” but both are absurd claims.

Dempster’s Pitch F/x data looks too similar to last year (similar velocities, possibly better movement) to say he’s lost a grip or some of his speed. Moreover, his strikeouts and walks are not out-of-whack, so basically everything has been held constant except his luck. His ERA is awful (8.05 ERA) but his FIP shows underlying success (5.75 FIP) and his xFIP wards off the luck beasts and shows the Ryan Dempster we know and love (3.92 xFIP).

Demp is fine, and last night was merely a portent of his play.