Sabermetric darling Nick Pivetta seemed to be a good bet to “break out” in 2019. If you’re a fantasy baseball player, he was a common pick as a late-ish round arm who could potentially pitch you into the playoffs, if all went right. His ERA pushed the 5.00 mark in nearly 165 innings in 2018, but ERA estimators universally pegged him about a run lower:

FIP: 3.80  / xFIP: 3.42  / SIERA: 3.51 /  CRA: 3.58

Both his K% and K%-BB% were just outside the top 20% off all SP to throw 150 IP. His Baseball Savant “Similar Pitchers” based solely on velocity and movement are Trevor Bauer, Justin Verlander, Chad Kuhl, Stephen Strasburg, and Gerrit Cole. No matter where you looked, the algorithms thought Pivetta’s true talent level was much, much better than the 4.77 ERA mark he had posted the year prior.

Fast forward to today. Pivetta has pitched 4 terrible games, leaving him with a 8.35 ERA, the most hits allowed in the entire league, and a sparkly new assignment to AAA. It has been, quite frankly, a disaster, and his pitching has probably single handedly cost the Phillies a win somewhere along the line, a win they will probably desperately need come September.

What is Nick Pivetta doing wrong? Nick Pivetta is fading his breaking balls as he falls behind - not trusting them, if you will.

Let’s take it count by count:

When Pivetta is ahead in the count (0-1, 1-2, etc.), his numbers are pretty standard. The strikes here don’t include balls hit into play, so we see he throws a few more strikes than league average when he’s ahead (which is good!) but nothing really jumps off the page.

More of the same when he’s even in the count (0-0, 1-1, 2-2). Pivetta throws a few more strikes when even in the count and his results on balls in play were actually exactly league average. Nothing to see here, either.

Bingo. When he falls behind in the count, Pivetta’s quality of contact allowed skyrockets. It moves so far past league average that I had to physically move the legend on the chart to avoid overlap.

Now, there are lots of way to be down in the count - 6 to be exact. Pivetta is down in the count about 25% of the time, which is only a hair better than league average. I attempted to isolate a few of these counts to find the driving force behind this xwOBAcon increase and was successful on my first try; the real culprit was hitter’s counts [i.e. 2-0 and 3-1 counts].

In hitter’s counts, Pivetta allowed a massive .620 xwOBA on contact compared to a 0.427 league average. This mark is the highest mark in the entire league of 109 pitchers who had 25 balls put into play on hitter’s counts since the start of 2018. It’s a whopping 52 points higher than Matt Harvey, who has the 5th worst mark out of those 109. Usually, I’d point to a pretty small sample size and say this could regress, but with a number as astronomical as 0.620, there’s something more here.

Let’s take a quick glance at Pivetta’s pitch usage and results from 2018:

The breaking balls are the sexy part of Nick Pivetta. He only throws the slider and the curveball about 40% of the time, but he gets great results with them, with a 34% whiff rate & .215 xwOBA on one and a 36% / .259 on the other. The fastballs presumably keep hitters a little off balance for the breakers, but by themselves, they don’t do a lot and the sinker can honestly probably get scrapped altogether, like most sinkers. The change doesn’t get thrown enough to really analyze. This also matches up well with Fangraphs pitch values from last season; the curve and slider got great results for Pivetta while the four seamer and the sinker especially got poor results.

That brings us back to his issues in hitter’s counts.

In most cases, Pivetta fastball usage is pretty typical, maybe even a little less than league average, which is good, given that it’s his curveball and slider that do the most damage for him. When he gets into a hitter’s count though, that fastball usage soars past league average - all the way above 85%! His sinker rate rises as he falls behind in the count as well, throwing it as much as 1 out of every 4 fastballs when he gets to a hitter’s count (typically it’s closer to 1 out of every 6 for him).

Pivetta slowly abandons his breaking balls a.k.a. his good pitches the further he falls behind the hitter. In a hitter’s count, he actually uses his breaker less than league average. This is undoubtedly a bad recipe for success for a guy like him, and it’s no wonder why he struggles so much when behind in the count. Stay true to your breakers!

I’m not sure what exactly why Nick Pivetta was sent down the Minors, outside of the obvious performance-based reasons. Perhaps that’s the only reason. Perhaps, and probably likely, the Phillies analytics team spotted something that isn’t outlined here and he needed a few starts to work on that something. Either way, it’s clear that his pitch usage in certain situations, or even in general, need a tweak. Scrapping the slider would be worth a try. However, the most important takeaway here is to keep his breaking ball usage well above league average in all counts, and learn to not fade them as he falls behind. Otherwise, the magic act of Nick and the Disappearing Breaking Ball may not be suited for the big stage in the long run.

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