Finding comparisons for Chris Tillman's sinker

Of the several high-ball pitchers that the Orioles employ, Chris Tillman is perhaps the most notable for his tendency to pitch up in the zone. I’m not at all sure why he does this when he a) pitches half the time in a park notorious for its homer-increasing effects and b) plays in front of a really good infield defense (at least on the left-hand side). But the fact remains his 39% flyball rate since 2012 is in the 80th percentile of qualified starters during that period.

So it was notable when, in July of 2015, Tillman began throwing a two-seam fastball (sinker) for what was just about the very first time in his career:

Tillman’s ERA, which was 5.03 in May and 5.13 in June, dropped precipitously to a sublime 1.31 in July as he had his best month in a long time. Many people noticed this correlation, including Camden Chat’s own Alex Conway and FanGraphs’ Eno Sarris. Unfortunately, either the pitch itself or the addition of the pitch didn’t help the rest of Tillman’s season. Despite throwing the sinker nearly 40% of the time in August, his ERA ballooned to 5.73 ERA that month. In September/October it was a ghastly 6.51 despite continued usage of the sinker. You can see how hitters began slugging better against it as the year went on:

Because this year is the first time Tillman really used the pitch, I wanted to see how similar it was to other pitchers’ sinkers. To do this I adopted the methodology that Jeff Sullivan used last year to compare Henderson Alvarez’s change-up to Felix Hernandez’s. I looked at the Baseball Prospectus PITCH f/x leaderboards for right-handed pitchers who threw at least 100 sinkers during the 2007-2015 time frame. I then calculated z-scores for velocity, horizontal movement, and vertical movement to find pitchers whose sinkers behave similarly to Tillman’s.

Velocity

Tillman’s sinker comes in at an average of 92.12 MPH. This compares favorably with sinkers from Tanner Roark, Brandon McCarthy, Trevor May, Tim Lincecum, Randall Delgado, Jason Berken (remember him?), Taylor Jungmann, Luis Mendoza, Juan Nicasio, Chad Bettis, Jesse Chavez, Drew Hutchison, Jeff Niemann, rotation-mate Miguel Gonzalez, Luke Hochevar, Lance Lynn, and Ian Snell. Phew. That’s quite a list and although it includes plenty of scrubs, there are a few diamonds in there.

Horizontal Movement

Tillman’s sinker moves an average of 6.71 inches from right to left. That’s similar to the movement on sinkers from Jair Jurrjens, Brett Myers, Tomo Ohka, Kyle Lohse, Tyler Chatwood, Aaron Cook, and (again!) Jeff Niemann. A fairly unimpressive list of pitchers, although Lohse is good and Chatwood is kind of okay. Kind of.

Vertical Movement

A sinker’s supposed to … sink. Tillman’s sinker sinks a lot, averaging a drop of 9.1 inches from delivery to the plate. This drop compares well with Carlos Villanueva and Matt Garza.

Z Scores

The z scores of these categories indicate how much Tillman’s sinker varies from the average pitch thrown by this group. A z score is neither good nor bad; it’s simply a measure of deviation from the mean. For example, his sinker’s velocity z score is 0.35. This score indicates his velocity is a bit more than a third of a standard deviation above the average sinker’s velocity. Put another way, his sinker is a bit faster than average but not by much.

His sinker’s horizontal movement has a z score of -1.28, meaning it moves more than a standard deviation less than the average sinker in this sample. Finally, the z score for vertical movement is 1.73. This score indicates his sinker sinks a lot more than the average.

If you combine these z scores together you get a value of 0.80. This indicates that, in terms of total variance from this group’s average sinker, Tillman’s sinker is just under one standard deviation away. That’s not nothing but it’s not inconsequential. But it’s not as interesting as the list of names of pitchers with similar sinkers:

• Yordano Ventura
• Hisashi Iwakuma
• Brad Thompson
• Shaun Marcum
• Jerome Williams
• Josh Tomlin

The first name that jumps out to me is Yordano Ventura, supposed-ace of the Kansas City Royals. He throws his sinker really, really hard (97.22 MPH) but it doesn’t have a lot of movement on it. Hisashi Iwakuma has quietly been a good pitcher the past several years; he no-hit the Orioles in 2015 and recently re-signed with the Mariners.

The rest of the list is the very definition of "damning with faint praise". Thompson had a replacement-level five-year career with the Cardinals and Royals, Marcum had a few good years but has been just okay since 2011, Williams has never been much above replacement level, and Tomlin has showed promise but has never really put it all together. These guys are somehwat-useful major-league pitchers, not stars or anyone you'd really hope to be compared to. Still, it's nice to know that Tillman's sinker isn't completely useless. It matches what we see from major-league veterans.

The comparisons get much better if you widen the definition of "comparison" just a little bit. Immediately beyond the above list you find two intriguing names: Carlos Carrasco and Raisel Iglesias. Carrasco has been excellent the past two years year with an xFIP of 2.66 in each season. He’s one of the more underrated pitchers in baseball. Iglesias had a good debut season with the Reds in 2015 and was recently identified as a 2016 breakout candidate by FanGraphs’ Tony Blengino.

Streeeeetch the comparision just a liiiiiitle bit further and you get Tyler Chatwood and Aaron Cook, who are nothing much to write home about. But you also get Chris Archer and Gerrit Cole, guys about whom you really should be writing home. The comparisons may be faint, but they’re there.

Maybe Tillman’s sinker didn’t have quite the impact on his 2015 season as fans might have hoped. It’s not an amazing pitch, and it’s not his bread-and-butter. But ground balls in OPACY are good, and there are signals that going forward he can generate more of them. There are even signs -- just a few, and they are remote, but they are there -- that his two-seamer has ace-like potential.