Stop me if you’ve heard about “enigmas wrapped in riddles surrounded by mysteries” before. Well, that was essentially Clay Buchholz’s 2012. Many fantasy owners hoped to buy low on Buchholz going into the year; fondly remembering his 2010 season while hoping the back injury that shelved him for more than half of 2011 was a distant memory. In ESPN leagues, he went 53rd among starting pitches (193rd overall) meaning he fell into the 14th-16th rounds in standard 12-team leagues. What managers couldn’t imagine was drafting a pitcher who could do more harm to their roto categories than if they had just started an empty roster slot. But that’s exactly what Buchholz was in April and May, putting up an ugly 7.19 ERA and dragging his owners down into the abyss. However, eventually the calendar flipped to June, and “good Buchholz” emerged from some sort of baseball cocoon, beginning a run that saw his 7+ ERA metamorphose into a 3.45 over the final four months of the season. Throw these two versions of the Boston righty into a cauldron and you end up with a guy 73rd in Zach Sanders’ 2012 rankings (below replacement value), but one who went from being completely and utterly unrosterable for more than eight weeks to a hurler who stabilized many rotations during the longest days of the summer.

So he was essentially two different pitchers in 2012: what caused the light to come on? Was there anything visibly different between Buchholz during the first two months and Buchholz from June on that answers the Jekyl and Hyde question? One obvious guess might be fastball velocity. After sitting in the mid-90s, with the occasion 97-98 mph four-seamer during his breakout 2010, he settled into the low 90s with his ceiling also a few ticks lower in 2011. 2012 was more of the same, however, and without a time machine, the days of Buchholz flirting with triple-digits might be long gone. In addition to yearly averages, there was little trend in velocity as the season progressed, so it wasn’t just a case of of early season rust falling off as the days clicked off the calendar.

However, if we dive a little deeper into his PitchF/X data, we do see some interesting data points emerge beginning in late May and early June. Here’s a plot of pitch velocity versus horizontal movement from Buchholz’s June 12th outing against the Miami Marlins:

A new pitch cluster! Sidebar: it actually didn’t first appear during this game, but had only occurred sporadically the previous few games — this was the first outing where Buchholz used this new pitch more than five times. Even more interesting than merely being a new cluster, it’s a new cluster you wouldn’t have even noticed if you just blindly followed the default PitchF/X auto-classification (which decided to call this something like a curvastange). If we ignore what MLBAM labels it and put the pieces together ourselves — similar horizontal movement to a four-seamer, velocity sitting in between a changeup and a fastball — we arrive at splitter. Splitter? Is that right? Thankfully, you don’t have to trust me, Providence Journal beat writer Brian MacPherson was able to get confirmation from Buchholz himself. In interviews, Buchholz told reporters he learned the splitter from fellow Texan Josh Beckett and was attempting to use it while he struggled with the feel for his changeup.

Now we have verification Buchholz starting toying around with a splitter in late May. Was it a useful addition? Below is a table of the usage frequencies of Buchholz’s three main offspeed pitches (CU = curveball, CH = changeup, and FS = split-finger fastball) along with the corresponding SwStr%. Thanks to the manual pitch classification by Harry Pavlidis at Brooks Baseball, we have reliable data on the actual splitters, not messy definitions like in the default data provided by MLB. Buchholz threw only three splitters in April and May, so the SwStr% values for those months are essentially useless.

What is apparent is Buchholz’s confidence in the splitter (>=5% usage) corresponds nicely with his rapid improvement during the June-September months. In addition, we see the splitter is an effective pitch, garnering more swings and misses than his curveball and almost as many as his changeup — which is widely considered one of the league’s best. Buchholz originally starting throwing the splitter as a temporary band-aid while his changeup was either missing or getting hammered (or both), but even as the swings and misses (and other peripherals) for that pitch came around in the second half of the year, the splitter became a more and more integral part of his arsenal.

So was the splitter’s addition the sole driver behind Buchholz’s resurgance after the first two months of 2012? Fairly unlikely. He still didn’t use the pitch nearly as much as his other offspeed pitches, especially earlier in the summer. In addition, there were other improvements in his rate stats that may be connected to Buchholz’s shift in offspeed repertoire, but not controlled by it. His walk rate dropped precipitously beginning in June (10.6% in April/May compared to 6.6% the rest of the year) and his .344 BABIP from the first two months eventually dropped to a season-ending .286 without a dramatic shift in batted balls, implying there was a degree of luck regression mixed in.

But what’s not arguable is the split was developed during a period when Buchholz was struggling with all his offspeed offerings and subsequently suffering in the box score (both real and fantasy) because of it. It’s a pitch he began throwing almost as a novelty, essentially as an emergency plan for his changeup. However, because of its effectiveness, it became a pitch Buchholz relied more and more on as the year progressed, to the point in August and September where he was throwing it near the same frequency as his more ballyhooed curveball and changeups. Buchholz won’t be drafted very high next year; probably for good reason. Between injuries and ineffectiveness, he just hasn’t been a full-season valuable commodity since 2010. That said, savvy owners would be wise to look at investing in him in the latter stages of 2013 drafts. Having an off-season to cultivate another piece of his repertoire might help Buchholz survive outings with a flat changeup where he used to get hammered, and it might help add a few more strikeouts to the ledger, too.