The Quirkiness of Left on Base Percentage

Trivia question, whom was the league leader in LOB % among qualified relief pitchers last year and can you guess his rate?

Hint, here's #2-10.

Name Team LOB% WAR
Craig Kimbrel Braves 92.20% 2.2
Luke Hochevar Royals 92.10% 1.2
Koji Uehara Red Sox 91.70% 3.3
David Carpenter Braves 90.20% 0.9
Neal Cotts Rangers 89.80% 1.8
Darren O'Day Orioles 89.20% 0.7
Rex Brothers Rockies 88.80% 1.1
Jim Henderson Brewers 88.40% 0.3
Tyler Clippard Nationals 87.80% 0.4

If you answered Houston Street at 99.5%, you'd be right, if not there's always next time. Fear not though, because there's a good chance most of us are in the latter. This may or may not come at as a surprise as Street did finish with a 2.70 ERA and 33 saves however most of his peripherals lagged behind. On the other hand Street was pretty bad last year, which I’ll get into in a second, and hasn't been truly dominant in some time. Since this is a SABR blog we can presume the latter is truer of his real talent.

Before I continue, for those who are unfamiliar with LOB. It stands for Left On Base rate and is not calculated on the raw numbers you might see in the box score but rather the formula is: LOB% = (H+BB+HBP-R)/(H+BB+HBP-(1.4*HR)). It represents the percentage of baserunners allowed that didn’t score. A typical/average LOB rate is around 70-72% and it’s not uncommon for good pitchers to exceed this and bad pitchers to fall below it. For more on LOB %, follow this link. However unless pitchers are elite or well below replacement level; major fluxuations from the 70-72% should be taken with a grain of salt.

So how does the 2nd worst reliever, according to FanGraph at -1 fWAR and career owner of a 76.3% LOB rate, have the highest LOB rate baseball? Well the answer is twofold, one; he became the epitome of an all or nothing pitcher against opposing offenses and two it’s the nature of how the formula is constructed.

To begin, Street had the highest HR/9 rate of his career and in baseball last year at a whopping 1.91. He allowed 17 Earned Runs this year, 15 of which came via the home run on 12 home runs. It's astonishing his Earned Runs were not higher with that many home runs. Yet this, contrary to conventional wisdom, coupled with my next point helped keep his LOB rate so high.

Since the formula is measured by baserunners, we can see Street actually didn't allow a lot of baserunners to begin with. In fact, he was tied for the tenth lowest amount of baserunners allowed as seen below. (Formula created is H+BB+HBP= BRA)

Koji Uehara Red Sox 33 9 1 10 5 43
Bobby Parnell Mets 38 12 1 17 1 51
Paco Rodriguez Dodgers 30 19 2 15 5 51
Neal Cotts Rangers 36 18 0 8 2 54
Casey Janssen Blue Jays 39 13 2 17 3 54
Jason Grilli Pirates 40 13 1 15 4 54
Alex Torres Rays 32 20 3 12 1 55
Jason Frasor Rangers 36 20 0 15 4 56
Greg Holland Royals 40 18 0 11 3 58
Jean Machi Giants 46 12 0 15 2 58
Huston Street Padres 44 14 0 17 12 58
Joe Nathan Rangers 36 22 1 10 2 59
Luke Hochevar Royals 41 17 1 15 8 59
Alfredo Figaro Brewers 49 9 1 22 7 59
Glen Perkins Twins 43 15 3 16 5 61
Brian Matusz Orioles 43 16 2 21 3 61
Craig Kimbrel Braves 39 20 3 10 4 62
Casey Fien Twins 51 12 0 28 9 63
Darren Oliver Blue Jays 47 15 2 24 6 64
Tyler Clippard Nationals 37 24 4 19 9 65
James Russell Cubs 46 18 1 21 7 65

I've cut the table off to relievers over 65 baserunners allowed, however if you'd like to view the full table, click here. So in essence Street give up hits, he gave up a lot of home runs, but when he did give up home runs they were mostly of the solo variety, thereby not affecting his LOB rate. Street had a one of a kind season, one we won't likely see again anytime soon. However going forward temper expectations, if his peripherals don't scare you off, the likely regression to his career 76.3 % LOB rate should.

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