The fall from grace has been a steep one for Jason Hammel, who has proved relatively ineffective for the Chicago Cubs since suffering a hamstring injury just before the All-Star break.
The starting pitcher looked glorious in the early part of the season, posting a 2.86 ERA with 9.1 K/9 and 1.6 BB/9 through 17 starts. He had arguably been one of the most dominant pitchers in the National League prior to his injury setback in July, which required no DL time.
Times were good, but the good times do not last forever.
He has since posted a 5.32 ERA in the second half of the season with a 4.86 FIP and opponents batting .286 with a .531 slugging percentage. He’s on pace to nearly double the total amount of HR surrendered in the first half of the season and has yet to exceed 6.1 IP in any start since July 3.
These are grizzly numbers, to say the least.
When pitchers go to pot, there are usually some basic indicators that begin to show in the data. Expected strike percentages drop, BB% inflates relative to K%, velocity fluctuates wildly while pitchers struggle with command. There are literally dozens of stats that can signal regression in a pitcher’s performance.
Curiously? Jason Hammel has almost none. The only real change in Hammel’s outcomes are most of the basics: SLG has inflated, BB% has returned to normal-ish levels and BABIP is no longer kind to him. Other than that? Most of his peripherals are on par either with league averages or career averages.
This makes Hammel’s 2015 season one of the most frustrating cases of “I have no idea what is going on” ever.
Firstly, when a pitcher is seemingly being shelled while his peripheral stats remain relatively unchanged, we can assume his velocity is down. A strong, hard throwing pitcher like Hammel could be relying on out-muscling batters but not executing his regular mid-90s power to back that style of pitching.
Interestingly enough, his velocity has remained essentially on track with career normals, as indicated by the chart above. So this isn’t the issue.
Perhaps Hammel is having difficulty keeping batters off balance by feeding them too many similar pitches in succession? For the sake of argument, we’ll look at his latest poor start: September 15 vs. the Pittsburgh Pirates.
Again, this chart shows that that isn’t the case. There’s a steady stream of fastballs, sliders, changeups, and the occasional curveball spliced in an attempt to keep batters uncomfortable. If pitching IQ and approach aren’t the issue, the problem lies elsewhere.
In the search for more answers, we have to consider the intangibles. Immediately, we have to investigate whether Hammel is tipping his pitches, which would certainly explain the spike in total hits and slugging percentage.
This is where things get a bit more interesting. Take a look at Hammel’s release point vs his spray chart in his latest start:
It’s obvious in the first chart that Hammel is not tipping his pitches with his release point, as there is a wonderfully tight cluster. What is interesting, however, is the variety of locations that Hammel is showing in the second chart; namely the pitches in the dirt. This could indicate that Hammel is still struggling with his plant leg, which suffered the hamstring injury just before the All-Star break. While I can’t quantify it, it could be a nagging issue as Hammel progresses through his season.
This could also explain the 4.4 percent spike in Hammel’s BB ratios.
Is it the catch all solution to what is hampering Hammel’s performance? Far from it. You could also argue that he is adapting his pitch grips, which could result in the spray chart you see above. I lend zero credibility to this theory, however. If you wanted to know, you’d have to ask him personally and I certainly don’t have him on speed dial.
Lets move on to another theory then. Is Hammel changing his pitch frequencies? Perhaps he’s leaning more on certain pitches or feels he’s lost command of the pitches that brought him so much first half success. Consider the chart below:
There are three things to take away from this chart:
- Hammel recognizes his struggles and is attempting to make adjustments to his pitch mix frequencies, especially in September. This makes sense as he used his regular mix frequency in August, which was one to forget. Pairing a fastball and a changeup at similar frequencies is a classic way of doing this.
- Hammel’s strikeout pitch, the slider, is still his go-to.
- In relation to his career averages, Hammel is using his curveball now more than ever. It still accounts for less than 10 percent of his total pitches.
Are any of these indicative of an underlying problem? Do we have a sniff at what could be holding Hammel back from producing the quality starts and the dominant results that he enjoyed in the first half of the season? Without cherry picking or making wildly unstable conclusions, the simple answer is no. There are discrepancies in the data, but none of them are concrete enough to draw conclusions.
The only concrete evidence I could find of regression was in Hammel’s second half zone plots. They’re as follows:
Hammel is pounding the hell out of the lower outside edge of the strike zone almost exlcusively whereas in the first half of the season, he was working upstairs more uniformly against both LHB and RHB. It’s a small gap, but one that can’t be ignored. See below:
That hot lower right side has a lot to do with the fact that Hammel relies so heavily on his slider for outs, but the data is obvious: Hammel took a more balanced approach to the strike zone in the first half whereas in the second half of the season, he seems intent on working down.
Worth noting is that Hammel has also pitched more in the second half of the season to Kyle Schwarber, who is a young catcher and not exactly the best pitch framer. His catching metrics indicate that he catches more strikezone pitches for called balls than any other catcher on the Cubs’ staff (16.7 zBall%) and received the fewest close calls as well (-11 +Calls).
This would obviously hamper Hammel’s results a bit and could even be the precursor to why Hammel is being hit harder than ever. With fewer close calls going to the pitcher, he must now throw the ball in more obvious strikezone locations, thus making him more hittable. Is it the ultimate problem that Hammel is facing? Probably not, especially with Schwarber seeing more time in LF, but certainly worth some brief consideration.
I’m not the only one who has noticed the strange discrepancies in Hammel’s second half performance, either. Zack Moser over at BP Wrigleyville also took the time to dissect this trend. It’s certainly worth a read.
The story of Jason Hammel’s second half is a confusing and complex one. While there is no glaring issue that is hindering his performance, there seem to be several small ones that are dragging him down. Pair a nuisance injury with forced adjustment and a tighter strike zone and you will see a decline in performance; this is not debatable.
However, correlation does not prove causation and putting a single stamp on Hammel’s second half regression may ultimately prove impossible.