The Baseball Effect

What is going on with zack wheeler?

There was some buzz in the offseason surrounding Zack Wheeler, but compared to today, there’s a stark difference in the general consensus on Wheeler. To some expectations, Wheeler has been a pretty big disappointment. The 2009 sixth overall pick has pitched to the tune of a 4.69 ERA in 119 innings. Not quite the same performance we saw last year when he posted a 3.31 ERA in 182.1 innings pitched. Luckily, for those who still believe that last year was the real Zack Wheeler, there is still hope, and a lot of potential. Wheeler’s 4.69 ERA is not exactly representative of how he has truly pitched this season. For example, his FIP (3.66), a stat that does it’s best to remove luck from the equation, is a whole run below his ERA. This is obviously very similar to last year’s mark, so why is there such a difference in the outcome?

So far in 2019, Wheelers WHIP is at 1.28, sixteen points up from last years 1.12. While not the biggest difference, this could reveal some insight into why Wheeler is not getting the same results he did in 2018. Zack has actually decreased his walk rate this season by fourteen points to 2.57. Yes, this is a positive, but based off his current WHIP, it means he is giving up more hits this year. Generally speaking, hits onviously tend to do more damage than walks, especially when they are homeruns. Although he has dropped his walk rate and increased his strikeout rate, Wheeler has also close to doubled his HR/FB rate from 8.1 to 13.7. This six percent jump could definitely be the source of his inconsistency in 2019.

Going further down the rabbit hole, we find that Wheeler’s fastball velocity is a tick up from 2018. This correlates with the increase in strikeouts, as well as homeruns. When a guy is throwing fast, its harder to catch up to the high heat, but when contact is made, the ball travels considerably farther the harder the ball is thrown (Especially in 2019). To back this up further, Zack is also currently giving up two percent more flyballs per BIP when throwing his fourseam fastball. This could potentially be accredited to the launch angle movement, as well as the fact the 2019 baseball has more loft than ever. Ironically, it looks like Wheeler is trying to adjust to the league ever so slightly.

When looking at Wheelers pitch usage, it seems he has traded in his split for his changeup, at least partially. In 2019 he has a decrease in his split usage by exactly 3%, and an increase in his changeup usage by 3.24%. It has become somewhat of a trend in the last year or two that pitchers have slowed their splitter usage with the notion that splitters, in particular, line up with the current swing path that most hitters are striving to achieve. Zack may very well be testing out this theory, although it doesn’t seem to be working all that well. Or has it?

While Wheelers flyball percentage on his fourseam has increased by just a few percent, his flyball rate when throwing a slider has dramatically increased by almost ten percent and his linedrive rate by four percent. The interesting thing is, his slider usage has only dropped by about .5%. So far in 2019, Wheelers Changeup, Curveball, and Splitter all have produced a decrease in flyball rate from 2018. As it stands, Wheelers fastball and slider are the reason as to why he is not getting the same results he was a year ago, but if his velocity increased and his usage of the two pitches didn’t dramatically change, what did?

In 2018, opposing batters slugged .289 against Wheeler’s slider. In 2019, they are slugging .437! The cause of such a dramatic change can be found when looking at Wheelers pitch movement. While his fourseam has arguably gotten better than it was in 2018, with an increase in velocity and movement (slightly), his sinker has dipped more than enough in the other direction to cause some friction. Last year, Zach had horizontal movement of 1.17 inches to the left (or away from a right-handed batter). This year, Zach is only getting .71 inches of movement on the same pitch. To go along with that, his slider velocity also increased, making the pitch less effective, in turn, with his fastball. Wheeler is basically throwing a fourseam fastball and complimenting it with a slower, more hittable version. At least he can say the adjustment on his changeup and splitter usage seems to be working. Maybe the slider is next.

Knowing Wheeler is now on the IL with some shoulder issues, there could be some explanation to the lack of movement on his slider. Even so, if he returns healthy and is able to continue having success with his Changeup, Curveball and Splitter, while contrasting with his improved fastball, there is no reason Wheeler can’t have a second half that looks similar to his overall 2018 numbers. Add on top of that, the potential for his slider movement to return to form and Wheeler could be a very nice mid-season acquisition in the coming weeks.