One of the oldest truisms in baseball is that, to be successful, pitchers need to pitch inside. Establishing the inside of the plate allows pitchers to more effectively use the outer-half of the plate — and get batters to swing and miss or make weak contact more often on pitches thrown to the outer part of the zone. But it isn’t easy to pitch inside. Pitchers who lack the ability to get away with throwing inside tend to stay away from that part of the plate for fear that hitters will drive those pitches for extra-base hits. This can lead to hitters cheating on outside pitches and can force pitchers to throw fatter pitches as a result of throwing behind in the count.
So who were this year’s best pitchers when it came to throwing inside? I dove into our PITCHf/x data and found out.
I kept the definition of inside narrow, so I only focused on pitches with a horizontal value of less than or equal to -.5 when thrown to right-handed hitters and greater than or equal to .5 when thrown to left-handed hitters. Essentially, I was looking at pitches on the inner-quarter of the zone, based on batter handedness.
I based the run values per pitch on Joe P. Sheehan’s early work from 2008. Joe originally broke out values by count, but for this study I took his values and calculated a weighted average based on how many times each count occurred during the 2007 season. The table below lists the final run values that were used:
The actual values today are likely a bit different — given the changing run environment — but this at least gives us a way to compare pitchers, even if the actual run values might be off slightly.
For each pitcher, I took the total number of pitch outcomes listed in the table above for 2012 and multiplied those outcomes by their respective run values. Add it all together, and you get their total run value (positive or negative) when throwing inside .
Here are your top-25 starters from 2012 (negative values are better):
Top-25 Throwing Inside to LHHs & RHHs: Minimum >= 150 IP
Clayton Kershaw was the best, posting a -2.1 Runs/100 (run value per 100 pitches thrown). Most of Kershaw’s success was based on his performance against right-handed hitters, where he posted a -2.3 Runs/100. He did post a negative run value against left-handed hitters, although he wasn’t as dominant (-.1). That was mostly due to his 1.5 ball-to-strike ratio. The only hits Kershaw allowed on inside pitches to lefties were a pair of singles.
Here is Kershaw’s 2012 on the inside part of the zone:
Mets knuckleballer R.A. Dickey came in second to Kershaw, with a -1.4 Runs/100, and was followed closely by pitchers such as Joe Blanton (-1.3), Blake Beavan (-1.3), Justin Verlander (-1.2) and Gio Gonzalez (-1.2).
It’s not surprsiing to see pitchers like Kershaw, Dickey and Gonzalez near the top of the list. But I admit it was a bit surprising to see Blanton and Beavan.
The 23-year-old Beavan started 26 games for the Mariners in 2012 and posted a 116 ERA- and a 125 FIP- — not exactly stellar numbers. But Beavan was actually better pitching inside to RHHs than was Kershaw (-3.6 Runs/100). He was, though, not so great when pounding the inside of the plate against lefties (5.3 Runs/100 and 4.7% XBH%).
Blanton was generally good when her thrw inside to both righties (-1.9 Runs/100) and yo lefties (-.4), but didn’t have a great year by most measures (121 ERA-, 101 FIP-). Both Blanton and Beavan are good examples that while pitching well inside might be necessary, it’s not sufficient for overall success.
So how about relievers (min >=50 IP)?
In a bit of a surprise, neither Craig Kimbrel nor Aroldis Chapman came out on top. The best at throwing inside? Rafael Betancourt. The 37-year-old Rockies reliever was dominant overall (63 ERA-, 70 FIP-), but especially so when throwing inside. He posted a -5.1 Runs/100 and didn’t surrender a single extra-base hit.
For the curious, here are the top-25 starting pitchers, broken out against right-handed and left-handed hitters:
Top-25 versus RHH
Top-25 versus LHH
A final caution: It’s difficult to analyze a pitcher’s performance on inside pitches in isolation from their other pitches. To some extent, if a pitcher is really effective when throwing to the outside part of the plate, then hitters will need to respect that. And that means hitters might cheat in ways that leave them vulnerable to inside pitches. An analysis that looks at how dependent throwing inside is on, say, pitches to the outside, would be interesting and could help us better understand why some pitchers are more dominant on the inner-quarter of the plate.
As for the truism about pitching inside, the correlation between Runs/100 and ERA- last year for pitchers who threw at least 50 innings was .52. Essentially, 27% of the variance in ERA- could be explained by how good a pitcher was on the inner-quarter of the plate. There’s certainly more work to be done here, for sure.
Additionally, these run values are not adjusted for park or for league, so these relative rankings might shift a bit if we incorporate park factors into the calculations. I might tackle this at a later date, but even with parks not factored in, this gives us a pretty good idea about the season’s best pitchers when it came to throwing inside.
Special thanks to Tom Tango and Jeff Zimmerman for help on this article. All erros are, of course, mine. Also, thanks to David Appelman, Eric Seidman, Brian Cartwright, Harry Pavlidis, and Jeff Zimmerman for database assistance.
Bill leads Predictive Modeling and Data Science consulting at Gallup. In his free time, he writes for The Hardball Times, speaks about baseball research and analytics, has consulted for a Major League Baseball team, and has appeared on MLB Network's Clubhouse Confidential as well as several MLB-produced documentaries. He is also the creator of the baseballr package for the R programming language. Along with Jeff Zimmerman, he won the 2013 SABR Analytics Research Award for Contemporary Analysis. Follow him on Twitter @BillPetti.