Pitching report: What’s behind Phillies SP Aaron Nola’s recent rough stretch?

Philadelphia Phillies SP Aaron Nola went from being on the fast-track to his first All-Star Game to one of the most hittable pitchers in the league. Michael Beller looks inside his downturn.

Author:
Michael Beller
Publish date:
Jul 17, 2016

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It doesn’t take a Ph.D. in pitching to figure out the very start in which Aaron Nola’s season fell off a cliff. Take a look at his game log, courtesy of Baseball-Reference.

Save for one bad start against the Nationals back in April, Nola didn’t allow more than four runs in any outing through June 5. He threw at least six innings in every start, aside from the start against the Nationals, notching nine straight quality starts from April 22 through the first week of June. At that point of the season, Nola had a 2.65 ERA, 0.99 WHIP and 85 strikeouts in 78 innings, his sights firmly set on an All-Star nod in his first full season in the majors. And then came the downturn.

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Nola made it through just 3 2/3 innings in a loss to those pesky Nationals in his second start in June. He wouldn’t make it out of the fourth in any of his next three outings, and while he finally broke that streak in his final trip to the mound before the All-Star break, Nola surrendered five runs on six hits in five innings, taking a loss—his eighth of the season—against the Royals. His 2.65 ERA and 0.99 WHIP ballooned to 4.69 and 1.28, and his All-Star dreams were dashed.

A difference this stark begs for an investigation. We see guys slow down all the time, or have a couple bad weeks in the middle of a strong season. Rarely does a pitcher shut down all comers for two months and then, without warning, turn into one of the most hittable pitchers in the league. From his June 11 start through the rest of the first half, Nola had a 13.50 ERA and 2.56 WHIP in 18 innings. Hitters racked up a .427/.490/.629 slash line against him. The worst pitcher in the majors could get through an entire season without suffering through a stretch like that, and Nola—based on his pedigree, performance at Triple A and stint with the Phillies last season, and first two years of this season—is far more the pitcher we saw in April and May, not the one we saw over the final six weeks of the first half.

So what gives? Why did Nola go from an All-Star trajectory to a liability? Thanks to the splits tracked by Fangraphs, we know a few mind-boggling statistics from Nola’s terrible run. His BABIP across those five starts was an alarming .515. That should be impossible, even in that small a sample. Fifty-one and a half percent of balls that were put in play against Nola in those five starts ended up as hits. I know it’s a little awkward to read a number like that spelled out, but I felt the occasion called for it. Even in a game as quirky as baseball, that’s an oddity that must be seen to be believed. His hard-hit rate, which to that point of the season sat at a comfortable 24.2%, jumped to 33.8%, a rate that would have him tied for the 22nd highest in baseball, if it reflected his season-long total.

To recap, we know that a comically large percentage of balls in play against Nola found holes during the run-up to the All-Stark break, in part because hitters are squaring up more of his pitches than they did through the first week of June. The other crucial stats here are Nola’s strikeout and walk rates. When he was going good, he fanned 27.2% of the batters he faced, while walking 4.8% of them. When things went bad, his strikeout rate dipped to 20.2%, while his walk rate climbed up to 7.7%.

In sum, Nola got hit harder, and more of those went for hits. In addition, a larger percentage of balls were put in play, and what may previously have been a harmless single or slightly more harmful double plated a run or two because more batters were on base via the free pass.

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That’s the what, but we still need the why. The first two areas we want to check are velocity and pitch usage, and here we find nothing helpful. Nola’s velocity was largely unchanged leading up to the All-Star break, though his sinker did bottom out at 89.8 mph in his final start, and he didn’t alter his pitch mix to a significant degree.

Maybe the issue is that Nola has lost the touch on one or more of his pitches. While he has four in his repertoire, he leans heavily on his sinker (or two-seam fastball) and curveball. Those two offerings account for about three-quarters of his pitches. He builds everything off the sinker, and the curve is his best out-pitch.

As you’d expect with as dramatic a reversal of fortune as Nola experienced, all of his offerings got knocked around the yard worse in his last five starts than they did in his first 12. Still, the change in opponent success against the sinker and curveball is shocking.

In his good stretch of the season, Nola limited hitters to a .246 batting average and .406 slugging percentage with his sinker. The curve was lights-out, with hitters managing a .131 average and .196 slugging percentage against the pitch. He had 10 times as many strikeouts (52) as extra-base hits allowed (five) with his curve in his first 12 starts of the season.

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Over Nola’s last five starts, hitters are 21 for 37 when the sinker is the deciding pitch of an at-bat. That comes out to a .568 batting average, accompanied by a .757 slugging percentage. His curve, which was largely unhittable through the first week of June, has been tattooed to the tune of a .316 average and .526 slugging percentage. He allowed more homers on his curve in his last five outings despite throwing it 250 fewer times.

Now we know what’s happening to Nola, and we at least have the start to the why. His sinker and curveball, previously the very root of his success, have been terrible over his last five starts. Whether he’s facing a righty or lefty, Nola wants to throw the sinker to the same part of the plate. He likes to bust righties in on their hands with the pitch, though he’ll occasionally use it as a backdoor offering. For lefties, the sinker appears to be a center cut or outer third fastball before it darts away at the last second. Below are examples of the pitch’s effectiveness against hitters from both sides of the plate.

via GIPHY

Don’t worry about where the catcher sets up on either of those pitches. His target is where Nola needs to throw the pitch for it to end up where he wants it, and that’s exactly what he got in both of these at-bats. Courtesy of Brooks Baseball, we can see that Nola peppered that spot with sinkers in his first 12 starts.

Here’s Nola’s sinker zone profile for his last five starts. It’s no mystery why the pitch has been a lot more hittable over the last six weeks.

Nola needs to live in to righties and away to lefties with his sinker. All too often in his last five starts, the pitch has found the middle of the strike zone. As much run as the pitch might have, that’s not the sort of offering a major league hitter is going to miss very often.

The issue with his curveball is different. Nola isn’t having serious trouble spotting it recently, though it has been up in the zone a bit more frequently than he’d like. The curve is experiencing a problem of movement. More specifically, it isn’t moving horizontally as much as it once did. Here, again courtesy of Brooks Baseball, is Nola’s curve’s horizontal movement by start. The higher the number, the better the pitch is moving.

This is what Nola’s curve looks like when he’s getting the desired movement.

via GIPHY

And this is what it looks like when he isn’t.

via GIPHY

The first curve has sharp break, both horizontally and vertically. The second one isn’t a terrible pitch of the cement-mixer variety, but it doesn’t have nearly the same break as the first one, and catches far too much of the plate when facing a hitter like Edwin Encarnacion.

There’s more good news than bad here for the Nola investor. First, there’s little reason to believe he’s tiring. This may be Nola’s first full season in the majors, but he threw 187 innings between Double A, Triple A and the majors last year. Second, an issue of command, which is what he’s experiencing with the sinker, is the one a good pitcher can fix most easily. Nola’s sinker is his foundation. When he gets the feel for it back, his entire repertoire improves by osmosis. This is a rough patch, not a paradigm shift. Now would be a good time to check in on his price tag.

Pitchers to watch this week

Vince Velasquez, Phillies

Nola isn’t the only youngster in the Philadelphia rotation who bears watching over the second half. Velasquez had to shut it down for a couple of weeks in June after leaving a start against the Cubs in the first inning, but he was able to return and make three more starts leading up to the All-Star break. He looked good in those outings, allowing a total of four runs while striking out 20 in 17 innings. Unlike Nola, however, the 24-year-old Velasquez has never thrown a huge number of innings in his professional career. He topped out at 124 2/3 between Low and High A in 2013. Last year, he threw just 88 2/3 innings with the Astros and their Double A affiliate. Couple that with the minor injury scare, and it’s easy to see why the Phillies will be monitoring his workload closely over the next few months. Velasquez himself said late last month that he wouldn’t expect to throw more than 150 or 160 innings this season.

Jake Arrieta, Cubs

Arrieta surrendered 15 runs in his final three starts before the break, and hasn’t completed seven innings since a win over the Braves on June 11. Teams have adopted an approach that forces Arrieta to work deep counts, and so far have been getting the better of him. He has been helping them out, too, by walking 3.4 batters per nine innings. We should always expect a pitcher of his caliber to adjust back, but the approach is nothing new, and we’ve yet to see Arrieta revert to his dominant form. He’ll get his first chance to do that against the Mets on Monday.

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Rick Porcello, Red Sox

After hitting a little speed bump in late May and early June, Porcello finished the first half with a flourish, winning his final four decisions while amassing a 3.12 ERA, 1.29 WHIP and 35 strikeouts over his last 43 1/3 innings. His uncharacteristically high strikeout rate from the beginning of the season has come back down to earth, but he has remained a reliable starter in all fantasy formats, and he should still be capable of giving his owners a 7.5 K/9 ratio from this point forward. He’ll make his first start of the second half on Tuesday against the Giants.

Hyun-jin Ryu, Dodgers

Ryu made his first start since the 2014 NLDS just before the All-Star break, allowing six runs on eight hits in 4 2/3 innings. We always stress that results don’t matter when a pitcher is on a rehab assignment, and while that isn’t entirely true once he gets back to the majors, fantasy owners would still be wise to give Ryu a pass. In his first two major league seasons, he was a useful starter in all formats, and the bet here is he ultimately pitches like a capable backend guy in leagues with 12 teams or more for the rest of the season. He’ll next take the ball Wednesday in Washington against the first-place Nationals.

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Gerrit Cole, Pirates

Cole returned from the DL on Saturday, giving up four earned runs and seven hits in four innings against the Nationals. The 25-year-old had been out since June 10 because of a triceps injury, but he showed no signs of that still nagging him in the outing against Washington. Cole has been an excellent pitcher since making his debut in 2013, but he always seems to leave just a bit to be desired from a fantasy standpoint. This season it has been in the WHIP department, where his 1.32 rate doesn’t exactly scream “ace.” Cole is slated to make his second start off the DL Friday with the Pirates hosting the Phillies.

Prospect watch

Braden Shipley, Diamondbacks

At 38–52, the Diamondbacks are one of the more disappointing teams in the league, and the latest example of how meaningless it is to win the off-season. The additions of Zack Greinke and Shelby Miller were supposed to solidify the rotation, while an offense led by Paul Goldschmidt and A.J. Pollock was expected to be among the best in the league. Greinke has been good, but not the Cy Young candidate he was for the Dodgers a season ago. Miller has been a disaster. Pollock suffered a season-ending elbow injury on the eve of Opening Day. As such, it will be the fifth straight year without the Diamondbacks in the playoffs.

This is not a roster devoid of talent, however, and the Diamondbacks have more reason for optimism in the near future than the average also-ran. We could get our first glimpse at part of the future in Arizona later this season, with Shipley tracking toward the majors. The 24-year-old righty, who ranged from No. 38 (Baseball Prospectus) to No. 77 (Baseball America) on the top-100 prospect lists entering this season, is having a solid, though not spectacular, year at Triple A Reno. In 112 1/3 innings, he has a 3.85 ERA, 3.73 FIP, 1.27 WHIP and 70 strikeouts. He’s a fastball-curveball-changeup pitcher, with the fastball/change combo his bread and butter.

Shipley threw 156 2/3 innings at Double A last year, and it’s likely the Diamondbacks won’t want him to go much beyond that this season. At the same time, they almost certainly want to get their first look at what they have in him as a major league pitcher. Shipley may not throw enough innings—if any—in the majors to have much fantasy relevance this season, but he’ll be worth a shot if and when the promote him to the majors. More likely than not, however, he’ll first land on fantasy radars in 2017.

GIF of the Week

Dellin Betances made his third straight All-Star Game, an unprecedented achievement for a non-closing reliever. AL manager Ned Yost called on him to protect a two-run lead in the seventh inning with Corey Seager, Daniel Murphy and Paul Goldschmidt due up. He struck out Seager, surrendered a single to Murphy, and got Goldschmidt to fly out harmlessly to center. Up came Nolan Arenado, he of the 23 homers and 70 RBI, representing the tying run.

This simply isn’t fair.

via GIPHY