Walk-Rate Breakouts Have Become (Almost) Non-Existent

Among starting pitchers who finished in the top 20 in Roto value this season, few were further under the radar on draft day than Blake Snell and Mike Clevinger were. Though Snell was the fourth-most productive starter in terms of Roto value (according to ESPN’s Player Rater) and Clevinger ranked 17th, neither were among the top 190 players in ADP in NFBC or ESPN drafts.

In addition to a surge in their totals of innings pitched, both Snell and Clevinger experienced surprisingly strong improvements in their walk rates. Free passes were a weakness for both of them in 2017, but this season, Snell trimmed his walk rate from 10.8 percent to 9.1 percent, and Clevinger lowered his from 12.0 percent to 8.3 percent. Both pitchers were already proficient at getting strikeouts and had done a fair job of avoiding homers. With even stronger skill sets heading into 2019, fantasy owners could see Snell and Clevinger as particularly appealing options in a pitching pool defined by uncertainty and risk.

But should we?

A look back at walk rate decreases over the past 10 seasons reveals that it is rare for pitchers to sustain a single year-to-year improvement, and it has become even more rare over the last three years. Before we start thinking about how to build our 2019 rotations around Snell, Clevinger and some of the other apparent 2018 walk-rate breakouts, we should consider how risky a draft-day investment in these pitchers could be.

What Is a Walk-Rate Breakout?

A year ago, Snell and Clevinger had double-digit walk rates, and both were ERA title qualifiers, yet if we restrict ourselves to looking at pitchers who meet those thresholds, there are few cases of pitchers having even a one-year walk-rate breakout over the past 10 seasons. For the purposes of this analysis, I have set the bar for a breakout fairly low. I started off by including all pitchers who had a season with at least 90 innings and a BB% of at least 9.0 percent going back to 2008. Just those two requirements limited the pool to 385 cases.

Then nearly half of those cases could not be used for this analysis, because the pitcher did not throw at least 90 innings the following year. Then I eliminated nearly one-third of the remaining 197 cases, because I did not want to include pitchers who had strings of consecutive years with a walk rate in excess of 9.0 percent and no substantial year-to-year dropoff, other than their first year in the string.

As you can see in the table below, that narrowed the pool to 132 cases. (Note: Each successive group in the table not only has to meet the requirements listed for the group, but also the requirements for all of the groups that precede it.) If I stuck with this group of 132 cases, I could only know which pitchers broke out for a single season. I had to narrow the pool further to include only those cases where the pitcher had a third consecutive year of throwing at least 90 innings. That gets us down to 78 cases.

However, not all of the 78 cases featured a pitcher who had a notable BB% decline between the initial season with 90 innings and a BB% of at least 9.0 percent and the following year. (Going forward, I’ll refer to this “initial” season as Season 1. The season with a notable decline right after Season 1 will be referred to as Season 2, and the one following that will be Season 3.) I defined a notable decline as a 10 percent drop from Season 1 to Season 2. To be clear, by a 10 percent drop, I mean a percentage change over the previous season. For a pitcher with a 10.0 percent BB%, that would require merely a season-to-season drop to 9.0 percent.

That gets us to 51 cases. The final cut was for those pitchers who did improve their BB% by 10 percent between Season 1 and Season 2, but the improvement had the appearance of a rebound from an aberrant season, rather than the achievement of a new level of skill. We are now left with 39 cases of pitchers who improved to a new level of skill in Season 2, even with a generous definition of what constitutes a notable improvement (i.e., a 10 percent drop in BB%). So how many were able to extend their breakout to a second season?

Walk-Rate Breakouts Are Rare

We are starting with a pool of 39 cases, with the first set of Year 3 performances going back to 2010, so even if every single pitcher in the pool sustained a breakout into Year 3, it’s fair to say that walk-rate breakouts don’t happen very often. I am defining a walk-rate breakout as a 10 percent drop in BB% between Year 1 and Year 2 and between Year 1 and Year 3. With this definition, only 8.0 percent of all the cases of a pitcher posting a 9.0 percent BB% or higher over at least 90 innings between 2008 and 2016 have resulted in a sustained walk-rate breakout. In other words, 24 of the pitchers in our group of 39 extended their breakouts to a second season.

The 24 breakouts were heavily frontloaded towards the beginning of this decade.There has been exactly one walk-rate breakout established in the last three seasons. Between 2015 and 2017, there were just five pitchers in our pool who made at least a 10 percent improvement on a BB% of at least 9.0 percent: Shelby Miller, Danny Duffy, Gio Gonzalez, Andrew Cashner and Dan Straily. Duffy was the only one to extend his improvement into a second consecutive year.

Perhaps Snell and Clevinger can reverse the trend in 2019. Our sample of 39 walk-rate breakout candidates has left us with only a few clues as to how likely this is to happen.

What Distinguished the Breakouts from the Non-Breakouts?

There were no clear patterns among the 24 pitchers who sustained a breakout in terms of change in velocity or arsenal. Even in looking at the roles that control (Zone%) and proclivity for inducing chases (O-Swing%) played in lowering walk rates, there is no obvious difference between those who sustained a breakout and those who didn’t. If there is a possible surprise here, it’s that both groups experienced a slight decline on average in Zone% from Year 1 to Year 2. Even as they were improving in BB%, neither group as a whole was getting better at throwing strikes. Both groups, however, got better at inducing swings at pitches outside of the strike zone.

Improving one’s control was also not particularly important to sustaining a walk-rate breakout. The pitchers in the breakout group saw a slight decrease in Zone% (-0.3 percent) on average in Year 3, but they typically got even better at inducing chases. Meanwhile, the pitchers who did not sustain a breakout typically declined in both Zone% and O-Swing% in Year 3. It seems that improving O-Swing% is important to both an initial year-to-year improvement in walk rate and extending the improvement to a second consecutive year, while improving one’s Zone% is far less important.

Still, if we are looking at pitchers coming off a Year 2 improvement in BB% (like Snell and Clevinger), it’s hard to tell from these results whether they will be able to sustain their breakouts. We may get some clues by looking at the largest Year 1 to Year 2 changes in O-Swing%. Three pitchers from the 2009-2011 cohort — Jeff Karstens, Clayton Richard and Brett Cecil — increased their O-Swing% by more than 30 percent from Year 1 to Year 2. Karstens and Richard further increased their O-Swing% from Year 2 to Year 3, and Cecil’s declined by less than two percent. The walk rate for all three pitchers stabilized in Year 3, with none experiencing a swing of more than half a percentage point. There were no pitchers in the non-breakout group who increased their O-Swing% by as much as 30 percent from Year 1 to Year 2.

On the other hand, even the biggest Year 1 to Year 2 changes in Zone% were not predictive of what was to come in Year 3. The only pitchers with double-digit changes in Zone% from Year 1 to Year 2 were Jeff Locke, Jeremy Hellickson, Cecil and Cashner. Even though Locke, Hellickson and Cecil all had sustained breakouts, Locke was the only one of the three to increase his Zone% in Year 2. Cashner was unable to sustain a breakout, yet he increased his Zone% by 10.1 percent in Year 2.

What Does This Mean for Snell, Clevinger and Others?

The clearest finding is that the pitchers who failed to sustain a breakout experienced drops in O-Swing% and Zone% in Year 3, but that doesn’t help us much in assessing pitchers coming out of Year 2. We can note that 24 — or 61.5 percent — of our 39 pitchers did succeed in sustaining their walk-rate breakouts, and we can be encouraged by that. We can also realize that, if this trend holds, there is nearly a two-in-five chance that Snell or Clevinger could regress in walk rate next season. If the recent dearth of breakouts is indicative of future trends, their chances for regression could be even greater.

For Clevinger, the drop in walk rate was easily the most notable improvement he made in 2018. Had he not made progress in this regard, his skill indicators would have closely resembled those of Sean Newcomb. In the recent 2 Early Mocks, Clevinger achieved an 87.9 ADP, but without the improvement in walk rate, he conceivably would have been much closer to Newcomb’s 176.0 ADP.

Snell at least has a 45.0 percent improvement in K% from last season working in his favor. Even so, he would have been a less valuable fantasy pitcher if his walk rate had still been hovering around 11 percent. He would have been a must-start pitcher, but his best-case scenario for production would have probably been something like the 2017 version of Robbie Ray (2.89 ERA, 1.15 WHIP), with the 2016 version of Danny Salazar (3.87 ERA, 1.34 WHIP) being one of the lesser possibilities.

If Snell is going to be one of the top 10 pitchers off the board (as he was in the 2 Early Mocks) and Clevinger is going to be a top 100 pick overall, they will likely need to sustain the improvements in their walk rates if they are to pay back their fantasy owners’ investments in them. Yet the possibility of a Salazar-like floor for Snell or a Newcomb-like outcome for Clevinger looms. Neither pitcher increased their O-Swing% by as much as 12 percent, so they were far from the extreme levels of improvement that may have catapulted Karstens, Richard and Cecil into a sustained walk-rate breakout.

An additional pair of pitchers, Nick Pivetta and Kyle Freeland, also deserve a closer look heading into next season. Pivetta decreased his BB% by 24.5 percent, and while Freeland would have just missed qualifying for this analysis, his 9.8 percent drop in BB% helped him to become fantasy-relevant this year. Owners may see some appeal in Pivetta’s high strikeout rates or Freeland’s aversion to hard contact, but with the risk of walk-rate regression, both should handled with caution on draft day.