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Is Matt Duffy breaking out of his slump?

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Looking for the signal in Matt Duffy’s noise

MLB: Boston Red Sox at Tampa Bay Rays Kim Klement-USA TODAY Sports

Matt Duffy has been struggling mightily at the plate, more than has been typical of the offensive slumps in his career. The question is: why?

When I looked into Matt Duffy’s struggles last week I thought it was related to power (or lack thereof) and his playing deep into a season for the first time since 2016, but that may not be the whole story. Instead, it may have everything to do with pulled balls in play, which was not an element of my initial observation.

Here’s what I wrote on August 21st:

Fundamentally, I don’t see a significant change in his process... nor do I see one in his spray chart (28.8% pull rate in the first half, 28.2% in the second half) or hard hit rates (31.1% in the first half, 23.1% in the second half), and yet the results haven’t been there.


If and how Duffy recovers from this extended slump will be an important story line through the final six weeks of the season, particularly with all the depth the Rays have at second and third base within their system.

Behind closed doors (on Slack) my colleague Ian Malinowski criticized my analysis, because although I did look for a deviation in the amount of pulled baseballs, I did not dig into the quality of those batted balls beyond hard hit rate. Based on his observation of Duffy’s at bats, Ian believed that was an opportunity for immediate improvement.

My first instinct was to wait and see whether Ian was on to something. Matt Duffy’s trend line, after all, was still mired in a dramatic slump that dated back to July 22nd as per his 30-day rolling average of wOBA. What could have changed since then?

But Ian said I needed to take a closer look, and he was right.

Since my article was published, Matt Duffy has begun to heat up. Here’s what happens when you reduce the rolling average from 30- to 15-games:

It’s only six games, but that’s a Matt Duffy on the rise, where the low point in the bottom right is August 20th.

Ian believed that Duffy’s road to heating back up had everything to do with how he was putting the ball in play. An increase in pulled line drives would be the key to success.

Folks, Ian was right.

The Good Duffy

Before we look deeply at the slump, let’s first look at those days when the going was good. This was Matt Duffy’s 416 batted balls in 2018 prior to The Slump (67 games, through July 1):

Through what was essentially the first half of the season, when Duffy had enough offense to be the beneficiary of a Rays social media campaign urging us to give Duffy our All-Star votes, more than a third of his pulled batted balls were in the air (64% GB-pull).

His batting distribution shows a tendency to go opposite field, but a fair amount of balls batted deep when pulled, providing a fairly even distribution.

And his “radial” chart for hitting shows a grouping of batted balls hit under or flared/burned which is typical of what Duffy does to find success at the plate. Through July 1, the batting line was a respectable .321/.365/.430.

The Slump

Here’s Duffy’s 224 batted ball results during the period we’re defining as The Slump (July 2 - Aug 20), a period spanning 34 games and including the All-Star Break:

Here the line drives when pulled have disappeared, with no flyballs whatsoever. Dating back to the beginning of his observed wOBA freefall on July 2nd, almost every single pitch Matt Duffy pulled was on the ground. It’s here I have to tip my cap to Ian, because his suspicion was spot on.

Overall, Duffy’s tendency to pull the ball remained, but here we see the power outage on display that was highlighted in my article last week.

Overall, Duffy would see hit batting line fall to .234/.316/.248 as his bread and butter — hitting radial flares/burners — diminished, and he began swinging over the ball more than typical.

The Return

Tampa Bay has been on a tear as of late, including an eight game win streak and a perfect home stand, sweeping the Royals (four games) and Red Sox (three games). Duffy went hit-less in Game 1 of those seven, and was given a day off on Game 2, but returned to action for the five remaining games and seemed to be a new man.

Duffy made contact 36 times over those five games dating back to August 21, including 16 balls put in play (Small sample size alert!):

It’s impossible to say anything definitive here, but we can at least observe that Duffy nearly matched his pulled line drive total from The Slump over the last five games, so there’s some hope he’s breaking out.

Then there’s the distribution of those batted balls (here I’ll use the standard spray chart instead of a heat map):

And good news, those pulled baseballs were all to the outfield: a 3-2 groundball that indeed went to Brock Holt in left field, and two sharp line drives.

Best of all, here we find no weak contact, with the number of topped baseballs limited (but even then among the four two went for base hits), and with the majority of his batted balls back in the flares and burners category.

As for the three pulled balls, all went for base hits: two flares/burners, and one topped. And importantly, there are no results with weak contact.

Indeed, it is noteworthy as well that Duffy has two batted balls (5.5%) grater than 100 mph over the past week, where her had only six such batted balls (2.6%) during his 34 game slump, as compared to 26 batted balls (5.8%) with an exit velocity of 100 mph or more in his 67 games prior to the slump.

Again, this is small sample size theater, but to the eye Matt Duffy looked better against the Royals and Red Sox than he had in some time. This exercise suggests that this observation isn’t crazy. Furthermore, Ian’s suspicion that the quality of pulled baseballs could be the key to unlocking the good version of Matt Duffy also seems like a valid hypothesis, and will be a trend I follow through the rest of the 2018 season.