Gerrit Cole and the Curious Case of his Fastball
Gerrit Cole is very good; to begin with. There is no doubt whatever about that. He’s been especially good since being acquired by the Astros, in what has amounted to a highway robbery of a trade. The important thing I should note is that the Astros’ front office is lauded for their use of analytics, as you may have heard, leading to their recent success (also all those years where they drafted in the top five helped).
This Ringer article (an excerpt of a book written by Travis Sawchik and Ben Lindbergh) brings forward something about Cole and how the Astros have changed his repertoire since coming from the Pirates:
By now, the next part is predictable: Cole threw more four-seamers and fewer sinkers and recorded a career-high rate of curveballs en route to his second All-Star season and top-five Cy Young finish. The Astros, Cole says, ‘highlighted the fact that my curveball’s my best pitch for me, which took six years for someone to finally tell me.’ He’d always had a top-of-the-rotation toolbox, but until the trade, he says, ‘I was just sometimes pulling out the wrong tools.’”
I’m not going to belabor that point, as the sinker was a pitch he needed to drop. However, I do want to focus on Cole’s deployment of his four-seamer. There is credible evidence that higher spin rate on certain pitches is a good thing. The four-seam fastball is one of those pitches, but it is especially effective when thrown up in the zone. That Driveline article spells it out, with higher spin rate, the less Magnus effect on the ball means that the ball doesn’t drop as much (see also: it appears to rise).
Cole has one of the league’s highest spin rates for his fastball, ranking in the 95th percentile and I’m in no way campaigning for him to stop throwing it. But, I do think there’s something that needs to be explored. Cole’s K/9 rate is approaching 14.0, which would put him at the highest K/9 ever recorded. With this uptick in strikeouts comes a side effect. Cole is giving up 1.6 HR/9, one of the highest in the majors among starters, and I think I know why.
The reason pitching up in the zone was avoided for so long was because the prevailing belief that if pitchers left pitches up in the zone, then batters would punish them for extra bases. Granted, pitchers are throwing faster on average than they ever have and teams didn’t have the information that they do now. I still think some truth lies in the teachings of older philosophies and Cole is a prime example.
I worked with FanGraph’s Splits tool to look at starting pitchers who threw more than 75 innings, possessed a K/9 rate of 11.0 or higher and a HR/9 rate of 1.2 or higher. The list is below
It’s really not a bad group of company but there are some concerning entries. First, I want to acknowledge Robbie Ray as the patron saint of striking out batters whilst giving up mad homeruns. Congratulations Robbie, my man. Second, Max Scherzer! That was the year in which Scherzer gave up more homeruns than he normally did and some wondered if he was still an elite pitcher (spoiler: he’s still an elite pitcher and his HR/9 dropped back to normal).
Then there is James Paxton and Danny Salazar. Both are extremely talented, if not oft injured starters. It’s hard to compare Cole to them because he has been so durable so far but I still think their appearances are more positive than negative. We can also place Robbie Ray in that category. He’s yet to put together a full healthy AND good season, it’s either one or the other. When healthy, these are starters that teams would want in their rotation.
The last two, the concerning entries, are Chris Archer and Shane Bieber. Archer used to be a young talent, but since 2016 he’s run into homerun issues with each year growing worse than the previous. He was traded to Pittsburgh and has been ineffective while the prospects exchanged for him have thrived in Tampa Bay.
Bieber is an ongoing situation. He was considered a top prospect in AAA by Baseball America with potential as a mid-rotation option or as a backend starter. Bieber’s problem last year was too many hits, which could be because he has great control and throws a lot of strikes. This year his HR/9 has spiked, offsetting a similar spike in his K/9, which is up to 11.23. The common thread with Archer and Bieber is that their four-seamers have lower spin rates than the other pitchers, shown below:
I’ll try to explain why Cole shows up at the bottom a bit later, but for now let’s look at Cole’s pitch location for his four-seamer to try and tease out the homerun problem.
Above are heat maps of Cole’s four-seam fastball. On the top is his 2018 season and on the bottom is his 2019 season. Now, we only have about half a season worth of pitches in the right hand heat map but we can see a slight change leading to the issues Cole is having with homeruns. The really deep red lies more towards the middle-middle part of the plate. It’s not going to matter how fast you’re throwing, hitters can still punish pitches on the heart of the plate.
Your response may be that Cole is simply leaving too many pitches in the middle, but there was a reason I showed you the 2018 heat map as well. Below is a line chart which shows how many homeruns Cole has given up yearly broken down by pitch:
In the year 2017, his last with the Pirates, Cole experienced an extreme spike in homeruns overall. This was probably because his fastball heatmap in 2017 looked like this:
That’s really not where you want the majority of your fastballs to be, in my not-so-professional opinion. Still, let’s take out 2017 and simply compare his Astro years (2018–2019) to his Pirate years (2013–2016). We aren’t even halfway through the 2019 season and Cole is on pace to at least match, if not pass, his 2018 four-seamer homerun total. Both those years would be at least double the most homeruns he gave up with his four-seamer while with the Pirates. To me, that is at least some evidence that his new approach is contributing to his homerun problem.
It may also help that Cole is now pitching a larger portion of his starts at Minute Maid Park, which is far more generous of a homerun park than PNC Park was in Pittsburgh (101 vs. 93 HR Factor, respectively). It still doesn’t take away the credible risk of pitching up in the zone poses to giving up homeruns.
I mentioned that I would try to explain Cole’s spin rate increase from Pittsburgh to Houston. The best I can do is point to this FanGraphs article, which addresses Trevor Bauer’s accusations of Astros pitchers doctoring balls to increase spin. Whether they actually are or not, there’s evidence that some teams, the Astros being one, have found some method that increases a pitcher’s spin rate. Legally or illegally, we may never know. Thus, we can see he’s not only changed his approach with his four-seamer but also improved it.
To try and wrap a bow on this, I’d like to say that Cole’s new approach with his fastball obviously works. His strikeouts are up and his fWAR total in 2019 is on pace to match or surpass his best season total of fWAR with the Pirates, which was 5.1 fWAR. He’s already done that once with a career high 6.0 fWAR last year. This is more of a word of warning that there are side effects to this new implementation of his four-seamer. This could be an outlier season like it was for Max Scherzer, but given this is now a second season of elevated homerun totals for Cole, we should watch to see how he adjusts. Can he limit the impact of this side effect, or will it continue to grow?
