A shell of his Cy Young-winning self, what's the matter with Rick Porcello?

After a masterful 2016 season that won him a surprising Cy Young, Rick Porcello has come crashing back down to earth this year. Was last year simply an anomaly?

It was only about eight months ago that Rick Porcello was on MLB Network, celebrating one of the most improbable Cy Young Award victories in recent memory. Say what you will about Justin Verlander and Corey Kluber being more deserving, there’s no question that Porcello, at the very least, had the credentials to be in the discussion. Even that was a departure from his solid and steady, though clearly not spectacular, career heading into last season.

With that in mind, it’s hard to determine which is the bigger single-season swing. Was it 2016 Porcello, who became a 22-game and Cy Young winner after six years as nothing more than a mid-rotation starter? Or is it 2017 Porcello, who is in the midst of the worst season of his career, just one year after his best?

Last year’s star turn has to be more surprising than this year’s fall from grace. After all, Porcello’s 2017 numbers are more in line with his career marks than what he put up last year. Through 18 starts, he owns a 5.01 ERA, 4.21 FIP and 1.48 WHIP with 102 strikeouts in 111 1/3 innings. What’s most interesting, however, isn’t his face-value decline. It’s the nature in which it has happened.

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Going back to his days with the Tigers, Porcello has always been a ground-ball specialist. That was partially why he was never able to realize his full potential in Detroit. When your success is dependent upon your infield turning grounders into outs, and you spend two full seasons with Jhonny Peralta at short, Miguel Cabrera at third and Prince Fielder at first, you’re probably going to see a few too many balls scoot into the outfield for base hits. Still, Porcello at or above 49% in all his seasons with the Tigers. While that tendency dipped in his first two years in Boston, he still posted a 45.7% ground-ball rate in 2015 and a 43.1% rate last year, en route to the Cy Young Award.

This season, Porcello’s ground-ball rate is down to 37.6%. His second-most recent start, a loss to the Twins last week, provides a good illustration of a typical outing this season. He wasn’t terrible, allowing four runs on six hits in six innings, with six strikeouts against two walks. Out of 23 balls in play, though, just eight were grounders. One of those grounders was a rocket off the bat of Miguel Sano that went for an RBI double. A majority of those grounders did turn into outs, but when just one of every three balls in play is on the ground, a pitcher is flirting with disaster.

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Now, it’s true that fly balls are more likely to be outs than grounders. Porcello’s 38% fly-ball rate last season undoubtedly helped him to a .269 BABIP. His fly-ball rate is even higher this season, sitting at 40.6%. The reason why a pitcher flirts with disaster when two-fifths of his in-play balls are fly balls, though, is because those are the ones that can sail over the fences. That fate has hit Porcello all too often.

Porcello has already surrendered 19 homers this season. He allowed 23 all of last year, and 25 in his first year with the Red Sox. At this rate, he’s going to cruise by both of those totals in late July or early August. No one pitch is the main driver behind his increasing home run rate. He has allowed seven homers on his two-seamer, four on his four-seamer, three on the slider and three on the change. Given the usage rates on those offerings, we can’t really point to one as most responsible.

What does stand out, though, is the sudden drop in usage rate for Porcello’s two-seamer. Like any pitcher’s two-seamer, Porcello’s has generated a lot of ground balls during his career. Before last season, the pitch enjoyed a ground-ball rate of at least 55.6% in every year of his career. Last year, it fell all the way to 44.8%. This year, it’s sits at 40.6%. His season-long usage rate of the pitch, just north of 32%, would be a career low for a full year.

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There doesn’t appear to be a numbers-based explanation for why Porcello would reduce the two-seamer’s role in his repertoire. The pitch’s velocity, movement and spin rate are all flat, year over year, since 2015. We can go back even further with the first two numbers, and we still find Porcello throwing the pitch with similar velocity and near-identical movement during his days in Detroit. The pitch, itself, is the same. The pitcher is different.

As we discussed earlier, Porcello’s ground-ball rate has hit a nadir this season, but it has been trending down since 2013. That year, he posted a 55.3% ground-ball rate. Since then, his single-season ground-ball rates, in chronological order, have been 49%, 45.7%, 43.1% and this year’s 37.4%. This is simply the culmination of a years-long trend, and Porcello has finally reached the tipping point, with respect to home runs, in a season where balls are leaving the yard at unprecedented rates. If Porcello is now a fly-ball pitcher, he picked the worst season in which to become one.