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)

Name	Team	H	BB	HBP	R	HR	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.