The accusations are on the table. As Gordon Edes reported on ESPN Boston, Jack Morris  said he thinks that Clay Buchholz  was throwing a spitter in his start against the Toronto Blue Jays last week, and we know the baseball world will be watching Buchholz closely when he toes the rubber on Monday night against the Minnesota Twins.
It’s not easy to test these accusations, despite the fact that every moment of the start was recorded on video and baseball creates more data than any sport. Those who have looked closely at the Boston Red Sox pitcher’s forearm have not decided conclusively whether it’s just sweat and rosin or if there is definitely something else going on there.
So let’s avoid the screen captures of sweaty forearms and try to find the spitball in the numbers. PITCHf/x gives us data for the horizontal and vertical movement of every pitch. We should be able to find the outlier in the data … if it exists.
The quest for a spitball is just the quest to find a pitch that looks different. A pitch that doesn’t fit in. A fastball that moves too much, since that’s what caught Morris’ eye.
To the right are all the fastballs from Buchholz’s May first start against the Blue Jays, plotted by X and Y movement.
The pitch in red is the pitch against Jose Bautista  that caught David Schoenfield’s eye. Unless Buchholz was cheating on every fastball, that pitch was perfectly “normal” on May 1. As Dan Rozenson pointed out on Baseball Prospectus, that pitch fits right in with other fastballs thrown by Buchholz and the rest of the league as well.
Drew Sheppard at FanGraphs overlaid that particular pitch against a pitch from last year in Toronto, and almost no difference was noticeable.
But what about those fastballs in green? They are outliers on the day with their near-10-inch horizontal movement, paired with wicked vertical movement and 93-94 mph gas.
Plenty of pitchers, such as Max Scherzer , have outlier pitches.
Those are excellent pitches — but they aren’t extraordinary. Max Scherzer , Matt Harvey , Jeff Samardzija  and Lance Lynn  all average more horizontal movement on their two-seamers than Buchholz managed with those three pitches on the day in question. Just take a look at the X- and Y-movement of the fastballs thrown by Scherzer in a start from last week against the Twins and two things should emerge quickly (see right).
First, Buchholz’s “strangest” two-seamers would fit right in the heart of Scherzer’s fastball plot. Second, Scherzer had two extreme pitches of his own, pictured here in green; nobody’s asking Scherzer these questions.
But let’s say those three pitches in green were out of the norm for Buchholz, if not out of the norm for the league’s fastballs as a whole. Let’s look at a start from last April, when things weren’t going well for the Red Sox pitcher.
We do see a fairly similar spread of movement, and once again there are outliers. But you might notice that the overall movement of the group was not as impressive — the outliers move just seven inches horizontally, and the heart of the cluster is closer to five inches of movement. There was no 10-inch pitch in that game at all.
Before we start shouting and pointing, though, there’s one last thing to do: zoom out further on his career. Buchholz has had some up and downs in his short career so far, and his pitches have changed some.
Brooks Baseball judges pitch classifications carefully, pitcher by pitcher, and its date has tracked Buchholz throwing a sinker since 2009. The average horizontal movement of that sinker, year by year is shown on the right.
Clay Buchholz ‘s average FB horizontal movement by year
Those famous sinking fastballs, darting low and away on May 1? They’d look right at home when measured against the fastballs Buchholz was throwing in 2009 and 2010, when the pitcher had some of the best stretches of his career. You’d think, if he was cheating against the Blue Jays, he’d have broken out the spitter in 2012, when he struggled in the worst year of his career.
Or maybe, as he suggests in this April game report, the two-seamer is a fickle beast. Like most pitches, it’s hard to throw it with the same movement every time. Sometimes it even disappears for a year or two at a time.
And then, when it’s on, it can be a pitch that’s so wicked it almost seems unfair.