What's Gone Wrong For Paul Sewald?

 

Courtesy of NJ.com

   Paul Sewald was stringing great performances together to start off the season, and had proven that he deserved to be put in higher leverage situations. However, once the calendar turned to May, his performance took a severe 180 turn (4.64 FIP), and was even worse once June hit (8.77 FIP). The questions that lie here are what went wrong, and what can be done to fix the issue.
   For most garden variety players, this can be written off as a simple case of a guy who was getting one over on hitters, and once those hitters made an adjustment to him, he just couldn't adjust back. However, I believe that Sewald has some good talent, and when all is well, he has the makings to be a major contributor toward what I think can become a revolutionary bullpen if used correctly.

   Despite this nice upside, Sewald clearly has had problems this season with pressing manners like the good old gopherball. Overall on the season, he has allowed an astronomical 1.46 homers per 9, and that seems to be the main culprit toward his struggles.

   To put things in further perspective, he hadn't allowed a home run until May 2nd. Since then, his HR/9 has been 2.31, literally the same rate at which he is walking batters!

   A big reason as to why he is allowing so many homers is that hitters are essentially reaching for the sky when they make contact off him. He has only registered a 24.7 grounder percentage since May 2nd, while he has allowed a crazy 54.5% fly balls. This all comes together as an average launch angle of 22.4 degrees.

   The average exit velocity of 88.6 MPH seems to suggest that he doesn't deserve to have been creamed like the homer rate suggests (and has a nice exit velocity allowed of exactly 90 MPH on fly balls and line drives).

   What I find interesting here is that Sewald's average exit velocity allowed on home runs is at 101.5 MPH. That is obviously a blistering speed, but ranks far lower than the league average on homers of 103.7 MPH. What is concerning though is the angle at which hitters are launching these homers at, as they are currently at a 29 degree launch angle.

   Only diagnosing the issue, but not offering a solution does not help, so that is what I'll attempt to do here.

   Sewald seemed to be mixing up his arsenal and keeping hitters on their toes during his nice start. However, things have changed since May 2nd:

	FB%	SL%	CH%
Before May 2nd	57.8	32	10.3
Since	63	28.5	8.6

Courtesy of Fangraphs

   As you can see, Sewald has been relying far more on his fastball, which is honestly, a league average pitch in terms of velocity (90.1 is currently 10th worst in the majors)and spin (2278 is 56th percentile).

   I don't blame him for throwing fastballs often, as the pitch was quite a successful one in April. However, he has been getting a bit predictable with it. It shows with how successful lefties have been against the pitch, as they have a .368 ISO against the pitch! Here's how he's been locating the fastball to lefties the past month and a half:

   And here is how lefties have slugged against his most commonly located fastballs (and the dreaded down the middle location):

   As much as this has been a problem, his location with his slider has been a far more concerning issue.

Before May 2:

Since

   There's honestly not a large amount of sample size for either one here, but it is apparent that Sewald has left too many sliders down the middle of the plate. You'll notice that he threw a far higher percentage of sliders in the lower-in part of the strike zone (from a right handed hitters perspective) and more middle-low. How did hitters do on those pitches?

   Yikes. Righties are having a field day with the slider in particular, as in those two locations, they have an ISO of 2.25! And no, I did not misplace a decimal. Funny enough, lefties still haven't done much against his slider.

   So the problem is that righties are teeing off against low and in sliders, while lefties are popping his fastballs over the fence.

   The solution would be to throw less fastballs against lefties and work on his slider location so he can keep it down and away from righties (which his slider location currently is likely more of a mechanical/release point issue rather than deliberate planning).

   However, here is his fastball usage against lefties:

   Before, he was throwing 60% fastballs against lefties, and since May 2nd, its been over 71%. That will be a simple fix, as he can start throwing in more sliders down in the zone (preferably ones that are out of the zone since he has a solid 35.1 chase % on the pitch even during this tough stretch).

   It also can't hurt to start throwing a few more changeups, as it could keep hitters on their toes. I won't say anything too crazy about increasing his usage, but maybe hovering around an 11-13% usage could be worth taking into consideration.

   Sewald has shown that he can be a very capable pitcher, and worthy of being used in high leverage spots. I think that if he makes the necessary adjustments (and starts to hopefully see his bad homer luck turn around), then he can certainly bounce back and be a great contributor to the bullpen.

   All stats and info are accurate as of June 17, and are courtesy of Fangraphs, Baseball Savant and Brooks Baseball