Starting Pitcher Walk Rate Over- and Under-Achievers

Here in the final week of April, sample sizes are starting to build up, but there is still a lot of statistical weirdness out there. Just in the walk rate leaderboard alone there are some confounding data for fantasy owners to ponder. Jose Quintana and Michael Wacha with double digit rates? Vince Velasquez among the lowest one-fourth? It’s like I hardly know these guys.

Not only are certain pitchers’ walk rates hard to trust, but the numbers underlying them are making little sense in some cases. The graph below validates a relationship that common sense would tell us is meaningful — that pitchers who throw more frequently in the strike zone issue fewer walks. Of course, it’s not a perfect relationship. Over the previous three years, Josh Tomlin’s 2016 season ranks as the stingiest in terms of walks (that green dot at the very bottom is his), even though his control was fairly average. He just happened to have been very good at getting hitters to chase pitches out of the zone. In that same year, Jimmy Nelson (in the upper-right hand corner of the graph) posted a 10.7 percent walk rate despite pounding the zone at a 48.4 percent rate.

Just as Tomlin’s green dot reflects a strong propensity for getting swings on pitches out of the zone, Nelson’s fire-engine red dot is an indication of his struggles to deceive batters on bad pitches. When he slashed his walk rate last season down to 6.6 percent, it wasn’t because he had better control. It was because he got hitters to chase bad pitches at a higher rate.

In this young season, there are several pitchers who have walk rates that make little sense — not necessarily because they are out of line with our preseason expectations, but because they don’t jibe with indicators of control and deception. The graph below shows the BB% and Zone% for qualified pitchers, as well as their O-Swing%, which is indicated by the color coding. The greener the dot, the higher the swing rate on pitches out of the strike zone, and the redder the dot, the lower the chase rate is on said pitches.

To return to the examples given above, Velasquez would appear to be a walk rate overachiever. He currently owns a 5.4 percent walk rate, which looks out of place given his 27.4 percent O-Swing%. He is throwing in the zone at a 47.1 percent rate, but Max Scherzer and Brent Suter have similar Zone% and BB%, yet are much better at getting hitters to chase bad pitches. Quintana and Wacha, on the other hand, are likely deserving of their inflated walk rates. Quintana’s O-Swing% is just 26.1 percent, and Wacha’s O-Swing% is an abysmal 22.1 percent.

 

The darker red dots towards the right-hand side of the graph are some of the more puzzling cases of possible underachievement. (Before looking at those, just take a quick peek at the dark red dot at the top of the graph. That’s Lucas Giolito, who is legitimately having some serious walk issues.) Brandon McCarthy and James Paxton are burdened with high walk rates despite Zone% rates in excess of 49 percent. Both are struggling mightily to get batters to swing at bad pitches, though this has generally been a strong suit of McCarthy’s. Paxton, on the other hand, has a career O-Swing rate of 28.4 percent, so significant improvement may not be imminent for him. Reynaldo Lopez and Bryan Mitchell (just south of Giolito on the graph) have had decent, if not strong, control. Both have had little luck with inducing swings outside the zone, but both have shown a better ability to do so previously. If Lopez in particular starts to show an improvement in that regard, he could be a consistent fantasy producer.

Luis Castillo, whose 9.2 percent walk rate is not as extreme as Lopez’s or Mitchell’s, still looks like it’s due for improvement. With a 44.2 percent Zone%, there is nothing wrong with his control, and his O-Swing% of 32.3 percent is well above the major league average of 29.2 percent.

Moving to the lower-left corner of the graph, there is a quartet of pitchers who are helping themselves with walk rate and WHIP despite subpar control . Patrick Corbin, Alex Wood, Noah Syndergaard and Zack Greinke have been the definition of effectively wild. That has long been a calling card for Greinke, but the lack of control is something new for the other three. All four have had a history of being able to induce swings on pitches that should be balls, so any regression they encounter should be mild.

More suspect is the low walk rate of Johnny Cueto, who is the lone red dot in the sea of green in the lower-left portion of the graph. His Zone% of 43.0 percent is merely average, and his O-Swing% of 26.9 percent is concerning. If there is a reason for optimism with Cueto, it’s that his O-Swing% has been above 32 percent in each of his six previous seasons. Though Cueto is due for all sorts of regression (strand rate, BABIP, HR/9), his O-Swing% is trending upwards over his last two starts. He is also not allowing much hard contact, so he may continue to be productive, even if his walk rate is due for some correction.