The 2017 Starting Pitcher Walk Rate Improvers

About three and a half years ago, I shared the bestest starting pitcher xBB% formula yet. Since I mentioned to you recently that I have been on an xEquation binge, I updated that bestest xBB% one too, of course. But as I was working on it with an additional variable, I realized that Alex Chamberlain had literally done the exact same thing about two years ago. That same thing was adding the 3-0% metric from, which is the percentage of plate appearances in which a 3-0 count is seen. So rather than take credit for developing a better version of my original xBB% metric, I’m now simply updating the coefficients of Alex’s equation.

xBB% = 0.564 — 0.484*Str% — 0.216*K% — 0.528*I/Str + 0.505*(3-0%)

Adjusted R-squared: 0.795

Str% — Strike Percentage | Strikes / Total Pitches
I/Str — Balls in Play Percentage | Balls Put into Play / Total Strikes
3-0% — 3-0 Count Seen Percentage | 3-0 Counts Seen / Plate Appearances

My adjusted R-squared is slightly lower than from Alex’s equation, as we used different data sets, both in terms of years and minimum innings. My data set was composed of the 2011 to 2015 seasons and all pitchers that threw at least 50 innings, for a total of 1,638 player seasons.

So let’s use this new equation to identify the fantasy relevant pitchers that should improve upon their 2016 walk rates, assuming all else remains constant (which is a silly assumption, I know).

2017 BB% Improvers
Name Str% K% I/Str 30% BB% xBB% BB%-xBB%
Martin Perez 63.6% 12.1% 34.3% 4.6% 8.9% 7.2% 1.7%
Felix Hernandez 62.5% 18.6% 29.8% 4.0% 9.9% 8.4% 1.5%
Jimmy Nelson 62.7% 17.4% 30.2% 5.8% 10.7% 9.2% 1.5%
Carlos Martinez 64.9% 21.5% 28.3% 4.1% 8.7% 7.4% 1.3%
Jaime Garcia 64.0% 20.2% 32.1% 4.7% 7.7% 6.4% 1.3%
Seth Lugo 64.6% 17.3% 30.8% 3.5% 8.1% 6.9% 1.2%
Jake Arrieta 63.2% 23.9% 26.5% 3.8% 9.6% 8.5% 1.1%
League Average 63.8% 21.1% 28.3% 4.6% 8.2%

Eh, you might quibble with my definition of “fantasy relevant”, but apparently my equation is so darn good that BB% and xBB% marks generally match.

So yeah, you probably aren’t considering Martin Perez for a spot on your fantasy staff, even in your AL-Only league, you might prefer a solid middle reliever. But his control didn’t decline as much as his walk rate suggests, he induces tons of grounders, and he possesses an excellent changeup, even if we have discovered that the pitch has a strikeout problem. He’s got a long way to go with that strikeout rate though to make him worth even considering, but at least there’s some reason for optimism.

Phew, it’s good to find Felix Hernandez on a positive list after he battled injuries and posted the highest walk rate and SIERA of his career, along with his lowest ever strikeout rate and highest ERA since 2007. Still, it’s not comforting to see that Felix threw a lower percentage of strikes than the league average. Not surprisingly, it’s his lowest Str% mark ever. While xBB% hints that it shouldn’t have been this bad, even an 8.4% mark is much higher than we expected and would have settled in second highest during his career. Combined with a drop in strikeout rate and questions about the health of his elbow, I’m concerned.

So much for Jimmy Nelson the sleeper. All he did was strike out fewer hitters, walk more, and see his ERA jump by half a run. He still gets grounders though, and features a good (albeit far less good than in previous seasons) slider. Since his walk rate shouldn’t have been this bad, and he’s still young enough to take a sudden step forward with his control, he makes for a reasonable cheap gamble in NL-Only leagues.

Though I’m a fan of Carlos Martinez’s overall skill set, I do fear he’s going to be massively overvalued given his ERA-SIERA gap of nearly a full run. That said, if he could get that walk rate below 8% and/or push that strikeout rate back up, he could post a legit 3.04 ERA without the aid of a hugely inflated LOB%. I’m not going to pay for that though.

The move to Atlanta certainly hurts Jaime Garcia’s value as the Braves infield defense is projected to be slightly worse than the Cardinals, while the Braves are forecasted to score many fewer runs. The parks are both slightly pitcher friendly, so little change should be expected from park factors. That said, Garcia’s walk rate spiked to its highest mark since 2010, but xBB% isn’t buying it — he should have been right in line with his history. And since his ERA spiked above 4.00, while his SIERA stuck below 4.00, he should come cheap on draft day and yield a profit.

While it’s anyone’s guess how many starts Seth Lugo gets this season, it’s almost a lock he’ll find himself in the Mets rotation for an extended period at some point given their fragile group of starters. Lugo has become famous on these pages for his insane curveball spin rate, though the pitch wasn’t enough to lead to a whole lot of strikeouts. But he threw strikes and avoided 3-0 counts quite well, so xBB% expected his BB% to fall more in line with his recent minor league history, sitting well below the MLB league average, rather than right at it. I wouldn’t call him a sleeper until that arsenal proves it has the ability to punch hitters out, but he’s obviously better than a 4.66 SIERA (and 4.54 ERA Steamer projection).

So Jake Arrieta suddenly lost the huge control gains he enjoyed from 2014 to 2015, but xBB% thinks it wasn’t as dramatic as the results would seem to indicate. Now coming off a season with an ERA above 3.00, he might come at a reasonable price for a change. I just worry what happens if the Cubs defense isn’t amazing as usual. No one could consistently post BABIP marks in the .240s right?! Especially pitchers that have shown no such ability to limit line drives or induce pop-ups.

Mike Podhorzer is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year. He produces player projections using his own forecasting system and is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. His projections helped him win the inaugural 2013 Tout Wars mixed draft league. Follow Mike on Twitter @MikePodhorzer and contact him via email.

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7 years ago

Pardon me Mike, but regarding Garcia’s move to Atlanta: can you please explain to me how you can know what the new Braves stadium’s park factors will be? Have you seen the stadium or a diagram of it already?