May 08th, 2020

xBA on Fastballs vs. Breaking Balls, Part 1

​In previous posts, there has been a focus on the difference in expected batting average between fastballs and offspeed pitches. Let's turn our attention to the hammers, the Uncle Charlie's, the slurve's. Rather than create tables, here's a scatter plot as an introduction: 

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Ian Happ struggles on fastballs, but hits breaking balls well, bucking the trend.

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The y-axis is the expected batting average on fastballs, and the x-axis compares the xBA difference between fastballs and breaking balls. This scatter plot is interactive here with options to search by player, league, and even position. One key item of note: amongst relevant fantasy players), the average xBA on fastballs was .276 in 2019, and the average xBA on breaking balls was .222.

The most consistent hitters have a difference within 40 percentage points - guys like DJ LeMahieu, Cody Bellinger, and Mookie Betts. These are the green circles. The yellow circles represent players that don't fare well against breakers, but absolutely pummel fastballs, more than making up for breaking deficiencies. Nick Castellanos, Nelson Cruz, and Marcell Ozuna are the representatives in this graph. There are also a handful of players that hit fastballs and breaking balls about the same, but don't do either particularly well. These few are also captured in yellow. Finally, the red circles the players who a wide gap in their xBAs. We talked about Ian Happ before (his weakness is fastballs, so he shows up in both offspeed and breaking ball analysis), so let's extend the analysis further.

There are plenty of players to investigate, but let's start with a few oft-injured players:

Aaron Hicks (NYY - OF)
2019: xBA FB: .241; xBA BB: .116

It's worth getting excited about Hicks being able to play mostly a full season in 2020, given that he was a 5.0 WAR player in 2018, which was his first relatively healthy season in the bigs. But even in that season, he struggled with breaking balls, as he had a .202 xBA on them. Hicks whiffed on breakers over 40% of the time in 2019, compared to under 20% on fastballs.

​Hicks saw 55% fastballs last season, right around the average for fantasy-relevant hitters. That was a slight decrease from 2018. More importantly, he saw an uptick in breaking balls in 2019, as pitchers realized he struggles with them. Bet on the increase in breaking ball mix to continue, and do not expecting him to hit above .245 moving forward.

Justin Upton (LAA - OF)
2019: xBA FB: .246; xBA BB: .190

Is Upton starting to show cracks in his armor? After a few injuries in 2019 which limited him to 63 games, Upton had trouble with the bat (92 wRC+). Upton swung and missed at breaking balls nearly 46% of the time, compared to just under 22% on fastballs. Dating back to 2018, this gap was smaller (38.3% and 27.3%, respectively). Upton has always struck out above the league average, which should continue. However, his xBA on breakers back in 2018 was .257, which was above the league average. 

Upton saw an eye-popping 61% fastballs in 2018, well above the league average. That trend goes back to at least 2016. In that small 2019 sample size, Upton saw 54.5% fastballs. Upton has posted a .365-ish xwOBA since 2016 on fastballs. Yes, he has hit breaking balls well too, with the exception of last year. With the downward trend in fastball usage by pitchers league-wide, and this concerning trend with J-Up, Upton may not make a full comeback.  Assuming Upton is fully healthy, he should hit right around .245.

Gregory Polanco (PIT - OF)
2019: xBA FB: .263; xBA BB: .131

Polanco has severely struggled with left shoulder issues, and played just 42 games in 2019 - a small sample. However, his 2018 stats are not much better - he had a .283 xBA on fastballs and a .180 xBA on breakers. The common theme is that the gap on whiffs between fastballs and breaking balls is 10%. Historically, Polanco has struck out a below league-average rate, but his strikeout rate will likely be above league average as he shakes off the rust.

Much like Upton, Polanco has seen 60%+ fastballs in the past, including last year.  His breaking ball mix should see an increase, given his sub-.200 xBA on these pitches the last three seasons. Based on this trend, a career-low in batting average is possible - think low .240s.

Let's shift to some healthy dudes.

Maikel Franco (KCR - 3B)
2019: xBA FB: .264; xBA BB: .207

Franco has shown so much promise, yet so much disappointment in his four-year career. Franco is the antagonist of the three true-outcome story (career 15.3% strikeout rate, 6.8% walk rate). But, it is safe to say that when does strike out, it's on a "secondary" offering:

Franco has always struggled with making hard contact, which is the reason his BABIP has been low, resulting in a low batting average. This is most evident on breaking balls, which Franco sees a ton of, relative to most hitters (35% since 2016). One slight adjustment could result in a breakout season, but that's been a theory for a few years now. The realistic conclusion is that these xBA's aren't all that bad, given the league averages stated above. He should hit a league-average .250 average with 20 homers over a full season - something available from a ton of players.

Jonathan Schoop (DET - 2B)
​2019: xBA FB: .266; xBA BB: .207

Schoop is the mirror image of Franco. Consider this fun fact:

Schoop is the only player I've seen to have a higher exit velocity on non-fastballs! He did this in 2018 too. His lack of hard contact also results in low batting averages; however, when he does make hard contact, he barrels the ball much more often than Franco does. So despite striking out at a significantly higher rate than Franco, we can expect a slightly higher average - somewhere between .255-.260. Schoop sees anywhere between 56% and 59% fastballs in a given year, and based on past seasons, that trend should continue. Much like Franco, Schoop's xBA's are just below the league average. 

The next post will focus on players who surprisingly have green circles, and may be overlooked heading into 2020!