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Orioles prospect season in review: Zac Lowther

The lefty deserves a mulligan after just 29 2/3 innings with Baltimore in 2021.

Texas Rangers v Baltimore Orioles Photo by Mitchell Layton/Getty Images

It was not a good year to be a rookie starter for the Orioles. As a unit, you were worth a collective 0.7 WAR. Your ERA was 6.50. You allowed 10.53 hits per nine innings. You walked one batter for every two you struck out (140 BB:258 K). And you definitely didn’t strike out many hitters, for that matter (258 in 324 IP, an unimpressive 7.17 K/9 rate).

Perhaps nowhere were the lost 2020 season’s effects on the Orioles more visible than when it came to the batch of pitching prospects who debuted in 2021 and struggled: Keegan Akin, Dean Kremer, Alex Wells, Mike Baumann, Bruce Zimmermann, and Zac Lowther. Though it’s impossible to say that any of these six really crushed it this season, it’s still likely we’ll see all of them back in an Orioles uniform in 2022. And that’s probably OK, because with the possible exception of Kremer, these rookies largely gave you the impression that what you were watching was a work-in-progress.

For Zac Lowther especially, it was a blink-and-you-missed-him 2021, with just ten appearances, six of them starts. Assigned to Triple-A Norfolk out of spring training, Lowther was recalled by Baltimore, then optioned the next day a whiplash-inducing four times from April to June, pitching just 5.1 innings through the first three months of the season. Lowther made just one start in this time, a disastrous 2.1 innings against Boston on May 8 where he got tagged for seven runs. Ugly.

The next time Lowther was called up, on July 2, he stuck with the big-league club a whole week, throwing two solid relief outings against LA and Toronto. It seemed like Baltimore was ready to give the bespectacled lefty a longer look. Right?

Wrong. Down Lowther went, returned to Norfolk in early July. Then he hurt his shoulder and wouldn’t be seen again in Baltimore until September 6.

It was that kind of season for him.

It wasn’t all bad news, though. Lowther was better down the stretch. In the first half of the season he made five appearances with Baltimore (one as a starter), posting an unsightly 10.80 ERA. He made five appearances in September, all as a starter, putting up an ERA of 5.06. In each half, his stats were distorted by one terrible start (against Boston and Toronto, respectively). Take out those two duds and Lowther’s first-half ERA is 4.50 and his second-half ERA is 2.36.

What to make of this abbreviated audition? Given the usual cautions about small sample sizes … maybe nothing. But Lowther’s career record of success in the minors gives some idea of his potential upside: a 2.61 ERA, 10.47 K/9, 3.13 BB/9, 6.55 H/9, and 0.52 HR/9 rate over parts of four seasons. MLB Pipeline views the former Xavier Musketeer as a “polished strike-thrower” with back-end starter potential who relies “on a combination of deception, pitchability and the magic of his ultra high-spin fastball.” Lowther’s slow-but-deceptive fastball gets a scouting grade of 55, and so does his “spike curveball,” while his changeup is just “serviceable” and his slider is a work in progress.

Interestingly, based on Lowther’s 2021 actual pitch usage, the lefty’s pitch mix has undergone, and may be still undergoing refinements. Lowther’s most thrown pitches were, in order: 4-seam fastball (54.1%), changeup (17.2%), curveball (15.6%) and then, but not so far behind, either, the slider (13.1%). Surprisingly given Lowther’s scouting report, it was the slider that was his preferred putaway pitch—and for good reason, since batters hit .338 against his heater and .444 against his changeup, but .167 and .150 versus the curveball and slider, respectively. Scouts be damned: give us more Lowther offspeed pitches!

Lowther’s season was, in some ways, a tale of two halves, which may reflect this alluded-to pitch tinkering. About the only thing he did well in the first half was strike out hitters: 12.2 of them per nine innings, which is well above his minors career rate of 10.47 K/9. This declined to 8.1 K/9 in the second half, though that’s still not terrible. Otherwise, Lowther’s walk rate got better over the year, though it was still elevated for him (1st half: 4.44 BB/9, 2nd half: 3.84, versus 3.13 in the minors). Same with hits: Lowther allowed a bloated 14.4 hits per game in the first half and 9.8 in the second half (both well above a 6.55 minors career average, though).

On the other hand, Lowther’s first half and second half don’t look as different when you get down to peripherals. A first-half FIP of 5.81 isn’t materially different from 5.37 in the second (and both are way better than his actual 6.67 ERA during this time). A 4.81 xFIP in the first half is even lower—and it’s almost indistinguishable from a second-half xFIP of 4.75. Plus Lowther had terrible batted-ball luck in the first half, with a .440 BABIP, and “meh” luck, .317, in the second. So maybe that’s a better reflection of the O’s No. 11 prospect’s potential ceiling.

Safe to say, the jury is out on Lowther’s 2021 performance. What we can say is that while the big lefty with the retro frames is having decent success at whiffing hitters, what’ll be crucial for him next season is to cut down on the hits and walks. If he can do that, the Orioles will find themselves 20% closer to a respectable starting rotation.

Previous 2021 Orioles prospect reviews: Ryan McKenna, Alexander Wells, Kyle Brnovich/Zach Peek/Jean Pinto, Yusniel Diaz/Rylan Bannon, Tyler Nevin, Terrin Vavra/Joey Ortiz/Anthony Servideo

Tomorrow: D.L. Hall/Drew Rom