Jeremy Hellickson made his living off beating his peripherals. It was really quite astonishing - here's this guy who threw a four-seam fastball in the low 90s from the right side and was mostly a two-pitch pitcher; now try to score runs off him. It was tough to score much against him in 2011 and 2012, his first two full seasons with the Rays.
Over those two years, Hellickson threw 366 quality innings despite the poor 15.9 percent strikeout rate and 8.7 walk rate. His ERA- was 78; his FIP- was 113. His results were 22 percent better than average; his peripherals were 13 percent worse than average. He did this without being a ground-ball pitcher (a 38.3 percent GB rate in that time period). The main drivers of his success were his low BABIP (.242), high strand rate (82.4 percent), and high infield-fly rate (13.7 percent).
Those things disappeared after 2012.
Despite improving his strikeout rate and improving his walk rate from 2013 onward, his results got worse. His FIP- at 111 is not far from his 2011-2012 value, as the increasing strikeout rates across the league are parallel to Hellickson's individual improvement. However, his ERA- currently sits at 124 for 2013 onward. Hellickson stopped inducing weak contact (.303 BABIP, 7.0 percent infield-fly rate, higher hard-hit rate). His strand rate also significantly decreased to 69.1 percent. Indeed, whatever skills Hellickson possessed to beat his peripherals evaporated after 2012.
Hellickson's tendencies with men on base have changed a bit
As the strand rate would suggest, Hellickson used to be pretty good with men on base and men in scoring position. Looking at the strand rate now, I just sort of assumed that he was now less capable of buckling down with men on base. That's only partially true.
For his career, Hellickson has allowed a .319 wOBA with the bases empty, a .314 wOBA with men on base, and a .291 wOBA with men in scoring position. In 2015, the trend was more exaggerated but still held. He allowed a .362 wOBA with the bases empty, a .296 wOBA with men on base, and a .258 wOBA with men in scoring position. Hellickson still buckled down - his strikeout rate went from 17.2 percent with the bases empty to 25.2 percent with men in scoring position. He was vastly better than average in this situation.
However, that's only 2015. Overall, it's the dingers that are the problem. Hellickson has been relatively bad with the bases empty, so despite his best efforts to strand runners, he allowed a lot of them. His HR/FB has increased more with men on base and men in scoring position compared to the bases empty state. It's especially worse with men in scoring position. When players get a hit with men on base, that hit is much more likely to be damaging than in the past.
Hellickson's declining popup rate
Hellickson's infield-fly ball rate sat at 16.2 percent in 2011. It has declined every year since. If a pitcher does not miss bats on a regular basis, inducing popups consistently is a good way to limit the strength of contact. Hellickson does not miss many bats (with the bases empty), so he has relied on being an excellent contact manager to succeed. Hellickson does not manage contact quite so well anymore.
From 2011 to 2013, Hellickson's hard-hit rate allowed, according to FanGraphs, increased from 23.2 percent to 34.9 percent, where it has hovered ever since. The league average hard-hit rate for starters in 2015 was 29 percent, so Hellickson is no longer better than average in this regard.
I investigated what's going on with Hellickson's declining popup rate. I'm not very confident in my findings, but I'll present what I found. For one, Hellickson's four-seam fastball velocity has declined a little bit from its peak in 2012 - about one mile per hour or so. For two, Hellickson is not going inside against lefties with his four seamer as much (or at least up and in against lefties and up and away against righties - I did not separate the following visuals from Baseball Savant by handedness).
From the catcher's point of view, the green blob area is smaller in the up and in location to lefties, as well as inside in general. Clicking around the zone profile on Brooks Baseball, it does appear that the decrease in that location is against lefties, not righties. Not coincidentally, that area is where Hellickson generates popups the most against lefties.
Where Hellickson stands with the Phillies
Hellickson was traded from the Diamondbacks to the Phillies recently. In general, those are both hitter-friendly stadiums, though the Diamondbacks' stadium is more hitter friendly. The pure change in location won't benefit him much. It could even hurt a little. As a righty, Hellickson will face more left-handed hitters, who have an easier time hitting home runs in Citizens Bank Park than Chase Field. With Hellickson's aforementioned homer problems, this could be an issue.
In addition, Hellickson is leaving a comfortable defensive situation. The Diamondbacks had a stellar defense, ranking first in DRS and third in UZR in 2015. The Phillies were 27th in UZR and dead last in DRS.
It's not all bad, though. Odubel Herrera, the Phillies center fielder, actually was quite liked by both stats. Aaron Altherr, who logged time at all three outfield positions, was also liked in his very small sample size. As long as the Phillies can put someone in right field who isn't awful, Hellickson will be in decent shape as a fly ball pitcher. It's the infield where most of the Phillies' defensive woes reside.
Regardless of the external factors present, Hellickson's route back to being a good major league pitcher goes through himself. His defense can't help and the park won't matter if he's giving up hard-hit balls and dingers everywhere.
. . .