Mariano Rivera is the best relief pitcher of all time, and his 20 year run of greatness has mostly been fueled by throwing one pitch. The dominance of Rivera’s cut fastball has been well documented, and you likely know that when the Yankees have the lead in the 9th inning, opponents are going to see cutter after cutter after cutter.
But, now, over in St. Louis, Rivera has an odd imitator of sorts. No, the Cardinals closer is not a cutter specialist; he doesn’t even throw one. Instead, Edward Mujica — the team’s emergency fill-in closer with Jason Motte on the shelf — is closing out games using an endless supply of change-ups.
Technically, Mujica’s off-speed pitch is categorized as a split-finger fastball, but there’s really not much of a practical difference between a hard change-up and a splitter. They aren’t all gripped the same way in the pitcher’s hand, but in terms of describing pitch movement, splitters and power change-ups are basically interchangeable. And Mujica is thriving by leaning very heavily on his split/change.
Here’s Mujica’s pitch selection by year since 2007, per PITCHf/x:
Mujica used to be a guy who pounded the strike zone with fastballs, kind of a reliever version of Bartolo Colon. He didn’t miss many bats and was an extreme flyball pitcher, which is not a good combination if you’re trying to keep runs off the board. So, in 2010, Mujica basically ditched his breaking ball and started leaning much more heavily on his split/change, throwing it 40% of the time, and it led to a spike in both K% and GB%. With the new approach, he went on a nice little run as a quality reliever.
When Motte got hurt, though, Mujica was thrust into the ninth inning for the Cardinals, and his solution was to just throw his best pitch as often as possible. For the season, he’s up to 65% off-speed pitches, and of late, he’s been even more extreme, throwing it 71% of the time in May, including a couple of outings where it was the only pitch he threw. Here’s his PITCHF/x plot from his outing on May 17th against the Brewers:
Mujica threw 13 pitches, all of them split/changes, all of them middle away. He used one pitch in one half of the strike zone, and he retired the side in order. And this is basically what Mujica does every game now. Here’s a couple of heat maps of the locations of Mujica’s 2013 split-changes, both to lefties and righties.
He doesn’t have Rivera’s ridiculous pinpoint command, so there are a few pitches spread around the zone, but you can see where he prefers to throw his off-speed stuff: down and away, and preferably more down than away. Mujica just pounds the bottom of the strike zone with a pitch that tumbles towards a hitter’s ankle, making it a pitch that is almost impossible to hit with any authority when it is well located, but he throws it for strikes often enough that hitter’s still have to chase it.
In May alone, opposing hitters have chased 54 of the 81 (67%) split/change’s Mujica has thrown, and they aren’t exactly hitting it well when they do chase; he’s gotten 20 foul balls, 15 swinging strikes and 10 ground balls on those 54 swings. Despite there being no real surprise as to what is coming or where it’s going, opposing hitters have been completely unable to do anything against Mujica’s off-speed offering. For the year, opponents are now hitting .136/.149/.242 against him, good for a .170 wOBA, and it’s not like he’s just feasting on right-handers hitters, as his wOBA platoon split is just .162/.180.
With a low-90s fastball and a track record as a journeyman middle reliever, he might not profile as a typical closer, and it might be natural to expect that fireballing youngster Trevor Rosenthal will eventually usurp the role from Mujica in the second half. However, Mujica’s ability to just pound off-speed pitches at the bottom of the strike zone — knowing that Yadier Molina can corral anything that bounces — has made him a surprisingly dominant reliever so far, and there’s no real reason to expect him to stop pitching well.
Ever since Mujica adopted the split-change as his out-pitch, he’s been a quality relief arm. Now that he’s featuring it on nearly every pitch, he’s looking basically unhittable. Game theory suggests that a pitcher needs to mix up his offerings to keep hitters guessing, but there’s not much evidence that opposing batters can hit Mujica’s split/change even if they go up looking for it. He might not be a conventional relief ace, but Mujica’s command of one really terrific pitch has turned him into one of the better relievers in the National League.