A Look at How Jake Arrieta Went From Downright Bad to Absolutely Nasty

Remember when a lot of Cubs fans got upset about an early July trade that sent one of their best-performing starters to an AL team in exchange for some pieces most people weren’t very familiar with? No, I’m not thinking of the Independence Day deal that sent Jeff Samardzija and Jason Hammel to Oakland last year.

The results have been so lopsided in the Cubs’ favor that many have already forgotten that they shipped Scott Feldman to Baltimore in exchange for Pedro Strop and Jake Arrieta on July 2nd, 2013. At the time, Feldman was 7-6 with a 3.46 ERA for a team that was lackluster at best. Strop had a 7.25 ERA and 1.701 WHIP and Arrieta had posted 7.23 and 1.775 figures.

For those who only scout the box scores and stat lines, it looked like a Tom Rickett$ sell-off to avoid re-upping with a bigger contract for a pitcher who was performing well. At its core, the lament did have some merits though; for a team that seemed so lost to trade one of the few bright spots was disappointing.

But that myopic view didn’t take into account the fact that Feldman was outperforming his peripherals. On the other hand, the pair the Cubs received in return had stuff for days and simply needed a change of scenery and a little tinkering. And while Strop has been a solid member of the ‘pen in his Cubs tenure, it’s Arrieta who has really come into his own.

Upon moving to the NL, Arrieta’s ERA (3.66) and WHIP (1.123) dropped dramatically, though his FIP actually increased from 4.61 to 4.94. But it was pretty clear the guy had potential to be really good if he could just stay consistent and avoid the injury bug that had bitten him early in his career.

After sitting out his first few starts in 2014, Arrieta broke out and never looked back. He set a career-high in innings pitched (156.2, 37.1 higher than previous best) and career lows in ERA (2.53), FIP (2.26), and WHIP (.989). There was some skepticism as to whether he could continue those trends into 2015, but so far things are looking really good, especially after Tuesday’s game against the Mets.

So what changed? Could it possibly be as simple as the cognitive recalibration precipitated by the move from Baltimore to Chicago? Well, that might be part of it, but if you look at Arrieta’s pitch selection you’ll see a stark change that took place the moment he began his tutelage under pitching coach Chris Bosio.

When Arrieta was with Baltimore, he was basically a fastball/curveball pitcher with a slider and changeup thrown in for effect once in a while. But upon arriving at Wrigley, a shift took place in relatively short order as the slider began to take over. The results speak for themselves.

Then again, calling it a “slider” really isn’t fair. If you know anything about Bosio, it’s that he’s known as a devotee of the cutter; Arrieta’s version of it has become a Frankenpitch of sorts that is so dirty that video of it has been deemed NSFW. Even its mashed-up name, the slutter, sounds unseemly and illicit.

The numbers in the pitch-type section of Arrieta’s FanGraphs page perfectly illustrate the dual nature of this pitch. In one section, it appears as though he tossed out the slider in favor of the cutter, but in the PITCHf/x section it’s basically the opposite.

Either way, what’s clearly evident is that the breaking ball has usurped much of his tendency to lean on the fastball, particularly the four-seamer. The cutter/slider went from barely 15% of Arrieta’s pitches in 2012 and 2013 to roughly 30% in each of the last two seasons.

But it’s one thing to have a nasty pitch in your arsenal and quite another to be able to locate it well. After all, being a great pitcher isn’t just about avoiding contact altogether, it’s about not getting hit hard. Since developing the slutter, Arrieta has increased his ground ball and infield fly percentage while decreasing his line drive, fly ball, and home run numbers.

The chart below shows the percentage of pitches Arrieta has grooved, or put in a hitter’s wheelhouse, over the course of his career. Two things about this stand out to me immediately: first, the groupings are much closer together in the past two seasons; second, there’s a bit more consistency and we don’t see the wild spikes evident in ’12 and ’13.


I wanted to examine the idea of consistency a bit more; repeatability is, after all, key to performance to any sport. For a pitcher that doesn’t mean throwing the ball in the same place every time, but rather, being able to have confidence in his ability to make the ball do what he wants and go where he wants. Constantly tinkering with grips and getting different results, then, is a bad thing.

The charts below illustrate (from top down) the velocity, horizontal movement, and vertical movement of Arrieta’s pitches season-over-season for the past several years. If you’re just looking at the overall averages from the graphs, you probably won’t notice much of a difference. But look a little closer and see if you pick up the same trend I did…



ArrietaVertMoveAs I noted prior to the chart showing his grooved pitches, it’s pretty clear that Arrieta has simply grown more consistent in these past couple seasons. Gone are the spikes from years past, replaced with smooth lines that tell me the Cubs righty has more faith in his pitches and his ability to throw them exactly how he likes.

A great example of this can be found immediately above on the vertical movement chart. I referenced earlier Arrieta’s disastrous campaign in Baltimore that season and then wrote about his increased use of the slider upon arriving in Chicago. Take a look at the dip from April to July of 2013.

The slider is a pitch that should break away and down from the pitcher’s throwing arm, but it’s evident from the chart that Arrieta was basically throwing cement mixers that weren’t doing what he wanted. Losing faith in the slider meant relying more heavily on the fastball, which saw a career-high 65.1% usage in 2013.

Now look to the first graph and check the giant spike that occurred during the same timeframe as as the loss of the slider. At the time of his trade to the Cubs, Arrieta had been grooving 25% of his fastballs. To professional hitters. While pitching in the AL East. In case you haven’t sussed out my point yet, that’s a bad combination.

But you know what? Fans should be awfully glad that he had hiccups early on, because it was exactly those issues that allowed the Cubs to pick him up on the cheap, like buying Apple stock for $2.22/share in September of 2001 before the iPod was first released (it’s over $126 last I checked). And now that Arrieta has mastered his pitches and regained his confidence, he’s gone from downright bad to absolutely nasty.

All the talk about the Cubs on a national level has centered around Kris Bryant, with some peripheral buzz about Anthony Rizzo (who should be a legit MVP candidate). Then you’ve got the storylines about Jon Lester’s inability to throw to 1st and whether Starlin Castro will finally be traded to the Mets (a narrative I’d like to beat to death with its own shoes).

Then, way down on the list, you’ve got the emergence of Jake Arrieta as a true ace-level pitcher. He’s going to have to prove that he can keep this up over a full season and it’d be nice to see him eclipse last year’s high-water mark for innings pitched, if not even the 180 or even (gasp!) 200 IP level.

If Arrieta maintains his current confidence in all of his pitches — particularly the nasty one with the dirty name — and continues to treat teams in the same manner as he did the Mets on Tuesday, it’s going to be impossible to overlook just how good he is. And that, my friends, will be pretty groovy.

Charts via Brooks Baseball.

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