Going Deep: A Postmortem on the Pitching Staffs That Regressed Most

Tim Jackson tries to figure out the cause of cold, hard regression for starting pitchers on the Phillies, Rockies, and Mariners.

The 2019 season is unofficially over for all but a handful of teams. The non-contenders are left with two realities: Individuals playing to make an early statement for 2020, and clubs meting out surging intrigue or despairing concern. It’s never fun to focus on disappointing performances, but it can be necessary. That’s especially true when those bad performances are like dogs howling into the night for large swaths of the season.

MLB’s newest baseball has had a lot of say in regard to statistical output this year — we’ve already got the most home runs the league has ever seen despite multiple weeks left on the calendar — and for as much as it’s been a boon for hitters it’s been a bear for pitchers. Some have felt it more than others. We’re seeing something equal parts terrible and special out of three clubs this year. Starting pitchers for the Phillies, Rockies, and Mariners have generated 3 of the 7 worst year-over-year staff performances since 2016.

A Tale of Two Seasons

In some sense, each team knew what it was getting into this year. Despite varying objectives for the 2019 season, all three clubs brought back the majority of their starters from 2018’s rotation. The Mariners brought back three pitchers who started at least 13 games last year; the Rockies brought back three who started at least 20 games, plus Antonio Senzatela, who started 13; and the Phillies brought back the same exact five primary starters, who all threw at least 24 games. While the rates here and after include the new starters, they’re largely carried by the guys who came back.

There was reason to believe in those players on each team whether it was because of their floor or their ceiling. Just 4 of the bunch — Felix Hernandez, Wade LeBlanc, Tyler Anderson, and Antonio Senzatela — had an xFIP worse than the league-average 4.16. Even then, they all at least appeared to offer a solid foundation for the back of the rotation. Others, in addition to their average or better xFIP, offered additional promise, whether it was high 90s heat or a breaking ball that fell off the table; things that are defining today’s game.

This year, league-average xFIP for starters is 4.49. Only 4 of the rotation returners — German Marquez, Aaron Nola, Jon Gray, and Jake Arrieta — have been better than that this year. This single-year hike alone provides some insight on how the new ball is causing nightmares for pitchers. But still, could we have seen this group’s lackluster performance coming?

K% Portending?

K% has a pleasant tidiness about it. You either got the batter to strike out, or you didn’t. It’s hard to fake so it’s a decent gauge of whether anything hinky is happening. For the most part, it jives well with how the Mariners were freefalling in the latter part of 2018, the Rockies seemed to be consistently onto something, and the Phillies, despite their collapse as a team, seemed like they had the most to buy into out of any of the three.

Now consider how these groups were whiffing hitters last year compared to this year.

Similar Process, Different Results

These are the three biggest drops in K% of any staff in the league. The average K% for the season is 22.8; last year, it was 22.3. The Mariners have gone from below average to worse, while the Rockies have gone from average to below, and the Phillies have lost the most ground in having gone from above average to below. Less whiffs inherently means more contact. How’s that gone for these pitching staffs? See for yourself.

More Contact, More Problems

No one’s given up more homers this year compared to last than the Rockies. The Phillies are 5th in that regard, while the Mariners are a more palatable 12th. These rankings make some sense given where each team plays its home games. Still, while progress isn’t linear, it would be tough to reasonably bake in such a steep downturn before the next upswing.

Seven of the 12 returning starters on these three teams have tweaked their pitch distribution in 2019 by throwing an offering at least 5% more. It might not seem like much, but that difference can determine whether hitters prepare to see it during an at-bat or not. The others have maintained a similar pitch mix compared to last year. Vince Velasquez, Antonio Senzatela, and Marco Gonzales have thrown more four-seam fastballs this season. Zach Eflin and Mike Leake are throwing more sinkers. Jake Arrieta tossed more changeups before he was shelved by injuries while Félix Hernández has thrown more curveballs. Only Senzatela, Leake, and Félix haven’t had much success with these new focuses.

Regardless of whether any arsenal tweak has worked out for a given pitcher, none of these individual examples quite provide us with insight into whether we could have foreseen their teams’ regression this year. They’re more a sliver of what’s gone awry; a tiny thread that’s been pulled among a big handful that’s undone a sweater. It’s fair to wonder if these players and teams will bounce back next year, especially knowing what we know so far about the new ball and how it’s already impacted them. The peripherals appear to tell us that they are largely what we’d think they are, even if those things are drastically different over the last two years.

Right now being a starter for the Phillies, Rockies, or Mariners means being in territory no one wants to occupy. These clubs are easy choices to keep tabs on as free agency and the trade market unfold through the winter. It might be smart to pay extra attention to the Ks their starting staffs can generate at the start of 2020 to get a sense of whether we should recalibrate our expectations for the rest of the season, especially with the consequences that result from giving up contact in this atmosphere. No matter what, this much is sure: There is plenty of ground for these clubs to make up again, and less to lose.

(Photo by Keith Gillett/Icon Sportswire)

Tim Jackson

Tim Jackson is a writer and educator who loves pitching duels. Find him in the PL Discord, editing, managing, and podcasting with @BREAKINGPodPL here or writing at Baseball Prospectus.

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