Reviewing The 2017 Starting Pitcher Walk Rate Improvers

In late January, I updated my pitcher xBB% was include and additional variable, 3-0%, which is the percentage of a pitcher’s plate appearances in which a 3-0 count is seen. Since Alex Chamberlain had already published such a formula, which built upon my original equation, I simply updated the variables of his. I then used the new formula to highlight a group of starting pitchers with an xBB% significantly lower their actual 2016 marks. This group was then discussed as potential walk rate improvers in 2017. Let’s see how they did.

Welllll, xBB% performed quite well! Six of the seven starting pitchers enjoyed improvements in their walk rate, with five of those six enjoying significant ones. Only Jaime Garcia saw his walk rate rise, and it was to a career worst mark.

Martin Perez had been alternating walk rates every season of his career, and then decided to settle in right around his career average in 2017. His walk rate is mightily important since he strikes out almost no one, so needs to be stingy with the free pass. Unfortunately, he typically isn’t, which is why just once has he posted a sub-4.00 ERA. With such a weak skill set, I’m not sure why he continues to be handed a rotation spot.

Injuries were likely to blame for Felix Hernandez’s decline in control in 2016, and although he was even less healthy in 2017, his walk rate rebounded. But heading into his age 32 season off a career low ground ball rate, declining fastball velocity, and now health being a question mark, he’s now a major draft day risk. Though at his cheap cost (ADP in the mid-200s), he’s seemingly worth the risk.

xBB% knew that Jimmy Nelson’s 2016 walk rate spike was a fluke, but of course there was nothing to suggest a major breakout was imminent. He cut his walk rate significantly this season and his strikeout rate surged. Unfortunately, he suffered a shoulder injury after diving into first base in September, ultimately leading to surgery, and will miss time in 2018. When he returns, who knows how his velocity and the quality of his repertoire are going to be.

According to my historical xBB% rates, Carlos Martinez has posted walk rates above his xBB% every year from 2014 to 2017. Although his walk rate did improve from 2016 to 2017 as xBB% predicted, he still underperformed by 1.2%. Given the degree of underperformance, it would seem that xBB% is missing something from Martinez, but it’s difficult to figure out what. He has been an outlier, but it does provide optimism for upside if he could correct whatever is causing his xBB% underperformance.

Jaime Garcia put on three uniforms this season as his control eluded him. He’s still got the grounders, but with a below average strikeout rate, it’s no wonder he posted his second straight ERA in the mid-4.00 range.

Seth Lugo had just 64 professional innings to his credit heading into 2017, and small sample size is where xBB% shines most. Lugo improved both his strikeout and walk rates, but a reversal in both his BABIP and LOB% marks meant his ERA skyrocketed, despite the skills growth. Unfortunately, this is closer to what he is, so he’s not much of a “better fortune” rebound candidate.

After his walk rate spiked closer to his pre-2014 days, many thought Jake Arrieta was broken. And although he did post his highest ERA since 2013, his walk rate dropped back down, though not to the levels of his 2014 and 2015 seasons. He continues to post suppressed BABIP marks, despite a batted ball profile that begs the question of how, which means he has now outperformed his SIERA marks for the fourth season in a row, three of which by significant margins.