Unpacking Zimmermann's '22 transformation into budding ace

April 28th, 2022

NEW YORK -- Three years ago, the Orioles watched gleefully as a young left-hander spent the early months of the season shining, blossoming into an ace behind a changeup-heavy arsenal and the element of surprise. That pitcher was John Means, whose unlikely ascent from unheralded prospect to top-of-the-rotation arm remains peerless during these recent pitching-lean years in Baltimore.

In what Bruce Zimmermann did this April, though, parallels are beginning to emerge. Perhaps they are the roots of a similar transformation occurring in real time. The latest example came Thursday afternoon, when there was plenty to like from Zimmermann despite Baltimore’s sloppy 10-5 loss to the Yankees at Yankee Stadium.

“Today wasn’t our best day defensively,” manager Brandon Hyde said. “We let down Zim.”

The five errors the Orioles committed (three behind Zimmermann during a pivotal fifth inning) were largely to blame for the lefty’s first loss of the season, marking the first five-error game in the Majors this season and Baltimore’s first since Aug. 8, 2018, vs. the Rays. All four runs Zimmermann allowed as a result were unearned, shaving his ERA to 0.93 through four starts. That ranks third best in baseball, behind only Marlins righty Pablo Lopez and Seattle’s Logan Gilbert.

The sample is admittedly too small for those results to be sustainable. But they’re certainly notable compared to 2021, when Zimmermann went 4-5 with a 5.04 ERA in 14 games (13 starts) while missing much of the second half with injury. At the very least, his recent body of work is sizable enough (19 1/3 innings, 80 batters faced) to suggest real growth from the Baltimore native.

“All of his pitches have improved,” Hyde said. “The command he has of four pitches right now, what he’s shown this season, is much improved from last year.”

How is Zimmermann doing it? Can he keep it up? Only time will tell. Let’s dig into the numbers in an attempt to answer those questions.

He’s throwing his fastball less
You may have heard of this happening, of pitchers across Major League Baseball benefiting from throwing fewer fastballs even in traditional fastball counts. Consider Zimmermann the latest convert.

Two-thirds of Zimmermann’s pitches Thursday were non-fastballs, led by his changeup (more on that later), which he threw 36 percent of the time. That’s in line with the kind of pitcher he’s been all season, during which he’s added a sinker but slashed his overall fastball usage by five percent. Opponents slashed .392/.367/.711 off his four-seamer in 2021; through four starts this year, they’re 11-for-20 (.556) against his two fastballs, and 9-for-47 (.191) against all his other pitches.

“There are so many good right-handed hitters in this division,” Hyde said. “As a left-handed [pitcher], you need to be able to pitch to both sides of the plate with quality offspeed stuff to keep them off your fastball.”

The changeup is improved
The trend of pitchers throwing their fastball less is rooted in what’s become a tenet of modern pitching philosophy: throw your best pitch more. For Zimmermann, that’s the changeup, which he’s throwing more (33 percent, up from 25 percent) and way more when ahead in the count (13.6 percent increase), especially against right-handed hitters (13.4 percent increase).

Plus, the pitch is just different. Zimmermann entered play Thursday throwing his changeup with 1.7 more inches of vertical drop and 1.5 more inches of horizontal break compared to 2021.

“That’s coming from the difference in wrist action and the intent I’m putting behind it,” Zimmermann said. “The action I’ve been able to get on it -- developing that pitch in the last five, six months -- I’m really happy with how I’m throwing it and confident in any count with it right now.”

He has also added two inches of horizontal run to his four-seam fastball, morphing it from a below-average pitch into a more competitive offering without added velocity.

“The big thing I see is the changeup development,” Hyde said. “The changeup for Zim has been key. From the dugout, there is really nice depth to it. It’s a big change of pace, getting big swings and misses from the right-handed hitters.”

Better command of his breaking pitches
The slider was an effective third pitch for Zimmermann last season, and he’s actually throwing it a little less in 2022, mixing it with his curveball about evenly. That unpredictability has been an asset. So has where he’s thrown the slider, as he’s shown the ability to locate it off the plate to get swings and misses with more regularity.

Look at Zimmermann's slider distribution from 2021, when he elicited a 36.8 percent whiff rate and a 22.7 percent put-away rate with the pitch …

… compared to 2022, when he’s thrown 45 of them and has yet to allow a hit on the pitch (All stats are updated with Thursday’s start, but heat maps are entering Thursday).