Where Did Sean Manaea’s Strikeouts Go?
I was a big fan of Sean Manaea heading into the season, believing that his above average SwStk% and superb minor league strikeout rates, would lead to a strikeout rate surge this year. Through April, my optimism was paying off, as he had struck out 23.6% of the batters he faced and posted a microscopic 1.03 ERA. Ever since that sparkling month, his ability to punch out batters has completely eroded. Why?
There are many reasons a pitcher’s strikeout rate could collapse. Let’s investigate several of those possible reasons, which include:
-A loss of velocity
-An unfavorable change in pitch mix
-A decline in the whiffiness of a particular pitch
Loss of Velocity
We’ll begin by comparing his velocities from 2017 to April 2018 to Post-April 2018.
| Period | vFA | vCH | vSL |
|---|---|---|---|
| 2017 | 91.0 | 82.8 | 78.3 |
| April 2018 | 90.6 | 82.2 | 79.1 |
| Post-April 2018 | 90.8 | 82.6 | 78.6 |
Manaea’s fastball and changeup velocity is down ever so slightly from last year, but clearly not by enough to explain anything. And if we’re just comparing his April to Post-April of this season, he has kept his velocity essentially stable, with a slight uptick on his two primary pitches. Of course, pitcher velocities do creep up throughout the year on average, so we would have expected this.
So far, his velocity doesn’t appear to be the answer.
Unfavorable Change in Pitch Mix
Now let’s go over his pitch mix over the three periods to see if perhaps this might provide an explanation.
| FA% | CH% | SL% | |
|---|---|---|---|
| 2017 | 53.7% | 34.5% | 11.5% |
| April 2018 | 53.2% | 26.8% | 16.9% |
| Post-April 2018 | 58.3% | 24.3% | 17.4% |
Okay, so now we see some changes. That does make sense, of course, as no pitcher perfectly maintains his pitch frequencies every season, or even during the season. In April, he threw about the same rate of fastballs as in 2017, but that rate jumped after the first month. Fastballs generate the lowest strikeout rate, so all else equal, you would expect that more fastball will result in fewer strikeouts.
In addition, Manaea’s usage of his changeup has dipped and he’s been throwing it even less than he did in April, which already represented a significant decline last year. That’s odd, because his changeup has consistently induced swings and misses, yielding mid-to-high teen SwStk% marks the last two seasons. He’s tried to offset the loss of changeup whiffs by upping the usage of his slider. The pitch actually generated a higher SwStk% than the changeup in 2017, but is slightly below this year.
So unlike his velocity, the pitch mix analysis did tell us something. Throwing more fastballs is typically bad for strikeouts, so that could provide a small piece of the strikeout rate decline explanation.
Decline in the Whiffiness of a Particular Pitch
Since we don’t have the ability to filter a pitcher’s SwStk% by pitch by date, I’ll resort to comparing Manaea’s SwStk% mark on each pitch from 2017 to 2018.
| FA | CH | SL | |
|---|---|---|---|
| 2017 | 6.8% | 17.2% | 18.7% |
| 2018 | 6.6% | 15.1% | 14.4% |
And there you have it. So not only is he throwing his worst swing and miss pitch more often, but his two non-fastballs have generated fewer whiffs. Both still remain quite respectable in that department, but haven’t been nearly as whifftastic as last year. We noted that the velocities have remained stable, so it’s perhaps a matter of movement or location.
Still sporting a solid 3.50 ERA, he looks like an obvious sell candidate. With a SIERA nearly a full run higher thanks to a .240 BABIP, and a lowly strikeout rate that has sat in the teens every month since April, he could easily deliver negative value the rest of the way.
Mike Podhorzer is the founder of ProjectingX IQ, an advanced fantasy baseball analytics platform that transforms projection data and in-season performance signals into actionable intelligence. He is the 2015 Fantasy Sports Writers Association Baseball Writer of the Year and three-time Tout Wars champion. He is the author of the eBook Projecting X 2.0: How to Forecast Baseball Player Performance, which teaches you how to project players yourself. Follow Mike on X@MikePodhorzer and contact him via email.
I’d have think Friers may start WC game on road or Cahill if we pull in front of Yankees. Too bad puk got injured…wed have 3 lefties in 19 and fiers and Cahill as #5 .
The other possibly related datapoints with Manaea are:
– BB% dropped from 3.12 to 1.81 from 2017 to 2018
– BABIP dropped from .318 to .240 from 2017 to 2018 (GB/FB were both 1.25)
To me, that suggests that he may be deliberately pitching to contact more and trying to minimize walks. In other words, if it’s intentional, then there are some advantages in aspects of his performance other than strikeouts. The question is whether the pros outweigh the cons. At least by FIP, he’s basically the same pitcher as he was last year.
Oh boy, didn’t take long before the “pitch to contact” theorizers made their way into the comments. Are you trying to tell me that Manaea wants opposing batters to make contact, at which points 24% of those balls in play will go for hits, and a bunch of those balls will fly over the wall? Because that’s crazy and no sustained successful pitcher consciously avoids striking hitters out.
And I don’t see how a low BABIP is related to a low strikeout rate. Are you suggesting low strikeout guys “induce weak contact”, thereby allowing a low BABIP? Because I’m pretty sure that’s wrong. If anything, I believe there’s a slight negative correlation between strikeouts and BABIP, meaning BABIP declines as strikeout rate rises.
But for whatever reason, manaea’s bb% is way down from last year, his k/bb ratio is better, and his xfip is down from 4.53 to 4.30. Whatever is happening to his k’s there’s no reason to believe he’s a less effective pitcher.
Mike, I agree that it can’t be summed up purely by a change of approach but there may be a slight effect here.
His Zone% is up 3%. His FStrike% is up over 2%. While these aren’t massive changes he is more of a strike thrower last year.
I haven’t looked to see if its a movement issue or where he’s locating his offspeed stuff but along with a noticeable drop in SwStrk%, there’s also over a 5% increase in his OContact% from 58-59% to over 63%.
This may be from him starting his breaking stuff more in the zone to induce more swings and therefore more weak contact or it could be a lack of movement. He has seen his soft hit % go up 1.5% but also saw his hard hit % go up by 2%.
Are these changes enough to explain the significant differences? Probahly not but it does suggest there is a move towards throwing more in the zone and maybe closer to the zone as suggested by his outside contact %. It could help explain the low BABIP and suggest its more sustainable since even if you make med/hard contact with pitches outside of the zone, its a lot harder to get hits. Increases in OContact I believe generally correlate with decreases in BABIP but this is more logical deduction
Ocontact% going up would presumably lower both k% and babip
We can maybe agree that pitching to contact is stupid, but I haven’t seen many people theorize that zero team ever suggests that to their pitchers ever ever. No one is talking optimal theory here.