Carleton: Are bullpen struggles contagious?

From Russell Carleton at Baseball Prospectus on September 27, 2016:

It’s been a tough September in San Francisco. That even-year magic that should have been carrying the Giants to their fourth World Series title in the last seven years seems to have left AT&T Park (our own Rob Mains has all the gory details).

We now hop into our time machine and travel back to September 4. The Giants were playing a day game at Wrigley Field, trying to salvage a split of a four-game series with the Cubs. Holding a 2-1 lead going into the bottom of the ninth, manager Bruce Bochy turned to Santiago Casilla, who had saved his 30th game the previous day. Casilla allowed a double to left field by Addison Russell, uncorked a wild pitch sending Russell to third, and then gave up a game-tying single to Jason Heyward.

Casilla escaped the ninth inning with no further damage, but the Cubs were eventually able to fly the “W” flag over Wrigley by virtue of another RBI single by Heyward in the 13th inning. It wasn’t unheard of for Casilla to blow a save. Even the best closers cough up a ninth-inning lead about 10 percent of the time, and for Casilla it was his sixth blown save of the year. But three nights later, Casilla couldn’t hold a two-run lead in the ninth in Colorado.


The panic that gripped the baseball world on behalf of the Giants was palpable and the damage done to the Giants’ playoff chances was obvious, but was this a run of horribly-timed bad luck or something bigger? There’s always been a bit of unease with questions like this among Sabermetricians. There’s the well-known XKCD comic which attributes all of sports analysis to narrative pasted atop a random number generator. Relievers pitch in small samples and small samples are subject to huge amounts of variability.

It’s possible that the Giants just had some horribly-timed luck. Or maybe there’s something to it. The narrative around the Giants during the month of September is that no one in the bullpen has any confidence any more. Is it possible that, after coughing up that many ninth inning leads, there was a contagion effect? Everyone got so nervous about closing down a game that the anxiety fed back on itself and, suddenly, Bruce Bochy had a bullpen filled guys who were “pitching scared”?

If the “random variation” hypothesis is right, then we wouldn’t expect to see one pitcher’s struggles impact others on his team. But if the effect does spread, we ought to be able to find evidence of that.

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Originally published: September 27, 2016. Last Updated: September 27, 2016.