Huston Street and the Fatigue Factor

Full disclosure: I was busy at work yesterday and witnessed the whole ninth inning debacle strictly through my cell phone notifications, so I have no first-hand account on how the inning actually unfolded (nor did I have any desire to rush home and watch the re-cap). I did, however, look at the box score to see if Mike Scioscia had any alternative to running Huston Street out there for the third straight game. From the looks of the parade of relievers he ran out there, the easy answer is likely "no". Still, I have long wondered if it's wise to pitch a reliever three straight days without rest and whether the alternative - bringing a lesser pitcher into a high leverage situation - was a worthwhile trade-off.

Using Baseball Reference's nifty splits tool, we can quickly see that Street is less effective without rest this season:

When pitching a second consecutive day, his ERA is 3.86, with a 7.7 K/9 and a 3.9 BB/9. When pitching for a third consecutive day, his ERA balloons to 11.80, striking out only 4.4 batters per 9 innings. Sunday was the 7th time this season Street has been asked to throw three days in a row. While 6.1 innings is a fairly insignificant sample, he still had a 5.19 ERA under those conditions before taking the mound yesterday.

In fairness, five of the seven times he's been asked to pitch a third straight day he's come through unscathed. He was even asked to pitch in a fourth consecutive game one time this year and struck out 2 batters in a clean inning. Still, his career numbers show he is far more hittable pitching back-to-back days:

Both this year and in his career, Street has done his best work with one day's rest:

What could Scioscia have done differently? Yesterday, probably nothing. Joe Smith had also pitched a third straight day, while the rest of the pen has been anything but automatic. Even with a three run cushion, I have a hard time blaming him for going with his relief ace, even in a diminished state. Going forward, I hope who ever is in charge of building this team looks at the data and constructs a more efficient pen, favoring arms capable of going multiple innings. Both Street and Smith seem to be wearing down as the season moves along, so building a pen that would allow them more frequent rest could be a huge boon for this team next season.