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Jake Arrieta May Be Dealing with a Mechanical Issue … Which Could Be Good News?

Analysis and Commentary
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Through his first eight games last season, Chicago Cubs starter Jake Arrieta allowed a total of eight earned runs and posted an average game score of 72. Where do you think this is going?

Through his first eight starts this season, Arrieta has allowed a much more concerning 33 earned runs, while achieving an average game score of just 45.

There are plenty of reasons to be concerned and plenty more to be optimistic (and we’ll cover many of them), but one thing is very clear at this moment in time: Jake Arrieta has not been good. Or, at least, that’s the case Jeff Sullivan is making at FanGraphs, and, as you might suspect, there’s a lengthy analysis to support it.


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At the beginning of the season, the primary focus on Arrieta was almost entirely velocity related. But as those issues slowly melted away (Arrieta’s velocity isn’t all the way back, but it’s doing better), the results have not returned. However, according to Sullivan, no switch has been flipped. Because, as we know, Arrieta wasn’t pitching well near the end of last season either.

Consider that, from May 25, 2016 until the end of the season (134.1 IP), Arrieta earned just a 3.95 ERA, with 3.97 FIP to validate it. And from June 27th until the end of the year (his final 99.1 IP), Arrieta’s numbers looked even worse: 4.44 ERA (4.51 FIP). For some, I have to believe that his strong postseason run (he really was quite good in October/November (which, thanks)) completely wiped the extent of his regular season struggles from our collective memory.

But here’s where things get tricky.

Last season’s struggles were primarily command-related. As we should all remember, Arrieta’s mechanics began to go “awry,” last season, leading to 9.6% walk rate (by far his largest with the Cubs). However, that’s not the issue this year (6.6% walk rate). Instead, Sullivan theorizes, it’s a contact-management struggle.

Using an eight-game rolling chart for ground ball rate, something has become increasingly and troublingly apparent:

And that is: Jake Arrieta’s ground ball rate is plummeting to his pre-Cubs depths. Check out the numbers, season by season:

2013: 40.4 GB%
2014: 49.2 GB%
2015: 56.2 GB%
2016: 52.6 GB%
2017: 40.2 GB%

When you combine the increase in fly balls (that rate is up exactly ten percentage points over last season and FIFTEEN(!) percentage points over 2015) with some lower velocity and an inflated HR/FB ratio, it’s not hard to see why Arrieta has already allowed half as many home runs this season (8) as he did in all of 2016 (16) through just one quarter of the starts. But we’re going to get more specific than that.


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In 2015, Sullivan reports, no other cutter in baseball was as valuable as Jake Arrieta’s. Fast-forward two years and no one’s cutter has been less valuable in 2017 than Arrieta’s. So … what the heck has happened? Well, in short, his mechanics may be screwed up.

Using Brooks Baseball’s charts, Sullivan noticed that Arrieta’s average horizontal release point has shifted towards third base by a noticeable amount in 2017. That, in turn, led him into taking a closer look at some of his pitches. What he found is pretty convincing.

You’ll have to head over to his article at FanGraphs for the stills, but Arrieta’s front foot is noticeably further over towards third base this season than it was at the beginning of last year and especially in 2015 (when he was at his best). So while, yes, pretty much everyone credits Arrieta’s (almost instantaneous) success with the Cubs to mastering his cross-body delivery (something the Orioles pushed him away from), it appears the pendulum may have swung back in the other direction. But here’s the good news: that’s fixable.

According to Sullivan, Arrieta is basically the same guy he was the last few years (pitches, mechanical quirks, pitch velocity, exit velocities, etc.), aside from the potentially too cross-body delivery. And, in the end, he believes both that Arrieta has pitched better than his current ERA suggests and, most importantly, that “this all should be fixable.” I don’t need to tell you how important it is to the Cubs season for Arrieta to be himself, but I will anyway: it’s IMPERATIVELY important – not only for the regular season, but more notably, for October.


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The Cubs need their second ace back, and it’s possible they just may get him.


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Michael Cerami

Michael Cerami is a Writer at Bleacher Nation, and you can find him on Twitter at @Michael_Cerami.

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