One thing that fascinates me is when pitchers make minor tweaks that have some unintended consequences on their pitches. Specifically we’ll be looking at curveballs. Even more specifically, we’ll be looking at the change in curveball movement from O’s starters.

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I first broached this subject from a more 30,000 foot level over at Baseball Prospectus, so you should check that out if you’re interested in seeing things from a larger MLB level. It also features a certain trade target that I’d be interested in targeting if I were in the front office, so it has a hidden O’s slant as well.

Today we’ll look at the same data (for the most part), though I’ve taken some steps to highlight the O’s in the visualizations you’ll see below. We’ll start with a quick primer on how to interpret the data presented below, then the data itself, and finally some thoughts.

The X/Y origin (the intercept at the center of the chart) represents the average movement of each pitcher’s 2013 curveball. It doesn’t matter whether that pitcher threw a big 12-6 curve or a slurvy number. that same point is the 2013 movement for their curveball. The data points represented on the charts indicate the 2014 movement for each pitcher’s curveball. The charts are normalized for handedness, so a pitch to the left of the center line on the left handed chart represents a curve that “broke” (horizontal movement) more in 2014 than it did in 2013. A pitch below the horizontal axis was one that “dropped” (vertical movement) more than the pitch the previous year. This same logic holds true for the right handed chart, though increased break would be signified by data points on the right hand side of the chart, as opposed to the left.

The size of each point represents the increase or decrease in whiff rate for the curveball in question. Larger circles indicate that the pitcher got a lot more swings and misses on the pitch in 2014 than they did in 2013, while smaller circles indicate a smaller increase, or even a decrease, in whiff rate from last season to this past one.

Finally, all O’s pitchers are highlighted in orange, so as to more easily identify how they compare to their peers. I would recommend using the tabs to view the right handed and left handed sheets as opposed to the dashboard for a bigger view of the pitchers in question. The last point worth noting is that if you hover over a specific data point, you’ll see all the relevant details for the pitcher selected.

So with all that said, lets’ dig into the numbers:


Starting with the left handed chart, we’ll see the only lefty starter on the O’s roster: Wei-Yin Chen. I’ve always had a soft spot for Chen, so looking at his numbers is particularly interesting for me. His curve dropped more than 2 inches more in 2014 than the previous season, though it’s worth noting that he threw fewer of them this year. Chen added a full mike per hour to his curve last year, though his velocity is still a few mph below MLB average. Chen throws his curveball a little less than 7% of the time, about half as much as his go-to breaking ball, the slider. Still, the pitch serves as a good change of pace for the lone lefty in the O’s starting rotation.

Among the right-handed O’s starters, Chris Tillman is the least exciting when it comes to this sort of thing. His curveball was nearly identical from 2013 to 2014, with the 2014 version breaking ever so slightly more (still less than half an inch more though). Tillman threw just 2.5% more curves in 2014, and those curves generated just 10% more swings and misses. The one noteworthy change for Tillman is that his 2014 uncle charlie came in more than 1.5 mph slower than the 2013 version of the pitch.

The other two O’s starters, Ubaldo Jimenez and Miguel Gonzalez, are much more interesting. Jimenez’s curveball was pretty awful in 2014, as he generated 59% fewer whiffs in 2014 than he did the previous year. Jimenez’s curveball is pretty low on the hierarchy of pitches that the expensive righty throws fortunately, so while there is some concern that his curve was awful, it’s not devastating necessarily.

Gonzalez on the other hand has some positive momentum heading into 2015. He threw 60% more curves in 2014, which is a great thing because his curveball whiff rate more than doubled last season. Gonzalez’s curve dropped an inch and a half more last season, though that’s without much change in horizontal movement. If Gonzalez can maintain that level of performance in 2015, he’ll have a good shot at maintaining his role as a mainstay in the O’s rotation.

These findings might mean a lot. Then again, they might not. At the very least they’re interesting, especially if you think changes in pitches from year to year are interesting like I do. What stands out to you in this data?

Jeff Long
Jeff Long

Jeff was the owner of the Orioles blog Warehouse Worthy, which focused on making advanced statistics a part of the conversation for the average fan. Outside of baseball, Jeff is a graduate of Loyola University where he received his Bachelor’s and Master’s in Business Administration. The Maryland native currently works for an Advertising Agency in downtown Baltimore. Previously a contributor to Beyond the Boxscore, he joined Baseball Prospectus in September 2014. You can reach him at