It speaks to the current nature of the Orioles’ rotation that, for the past several weeks, their most consistent starter has been Bruce Zimmermann. Reliable without being dominant, Zimmermann has been a stabilizing presence since returning from his brief Minor League “reset” in early May, routinely keeping the Orioles in games during some of their roughest stretches of the season.

That trend continued Sunday, when Baltimore did little to support its local product in the O’s 7-1 loss at Tropicana Field, their club-record 15th consecutive road defeat, completing their weekend sweep at the hands of the Rays. Backed by only one run on two hits of support, Zimmermann limited the damage and held Tampa Bay to three runs over 5-plus innings, before the Rays blew the game open against the O’s ‘pen.

"Zim gave us a chance to win," O's manager Brandon Hyde said.

In that way, Sunday’s loss was a microcosm of what the Orioles have received for weeks now from Zimmermann, who owns a 4.25 ERA over his past six games (five starts). Their rotation is less reliable elsewhere, with John Means still sidelined with shoulder issues, Matt Harvey’s production in freefall and inconsistency from Jorge López and Keegan Akin. Whether Zimmermann fits in as a long-term piece likely depends on how the rookie left-hander pitches in the months to come, now with double-digit Major League starts under his belt.

“He’s getting nice experience right now. I am impressed with Zim’s pitchability,” Hyde said. “He’s able to get through Major League lineups by changing speeds, not being predictable, and he’s doing a really good job in his rookie year.”

So … what’s working? And what’s not? Let’s zoom out to assess Zimmermann’s progress thus far, and his 2021 season to date:

What's working?

The breaking balls
Zimmernann’s fastball usage has declined drastically in recent weeks, and for good reason -- better results from each of his three offspeed pitches. There is the changeup, which Zimmermann uses most prominently and to offset his heater. But lately it’s been his slider and curve that are generating the most weak contact. Opponents are hitting just .164 (12-for-73) without a home run off Zimmermann’s slider and curve this season, including 1-for-11 on Sunday.

“The slider is what got me through those later innings today,” Zimmermann said. “Since I’ve been back up, I think I’ve done a really good job of having both of them. The last few outings I’m seeing a lot more success with my slider, which, coming up through the Minors, was always my out pitch. … We’ve done a good job of talking our game plans into using both of them based on the swing paths of the hitters.”

Control
Control was a strength of Zimmermann’s in the Minors, and he’s carried it with him in terms of limiting free bases. His three walks Sunday were something of an outlier, matching his season-high through 11 starts. He’s issued two or fewer walks in 10 of his 12 appearances, and 26 of 262 total batters for an above-average 7.6% walk rate.

Consistency
This is the category that matters most for the Orioles. And it’s been a strength of Zimmermann’s, especially as he’s pitched deeper into games since returning from the Minors last month. He’s completed at least five innings in five of six starts, holding opponents to two earned runs or fewer in four of those outings.

“I didn’t have my best stuff today, but with what I had and the guys behind me I did a decent enough job,” Zimmermann said. “I expect more of myself though, hopefully to get through that sixth inning next time.”

What’s not?

The fastball
Zimmermann's ability to limit the damage Sunday was notable because when he does allow runs, they can come in bunches: three in 4 2/3 innings April 21 in Miami, four in 3 2/3 innings April 27 against the Yankees and five in three innings May 22 at Washington, for example. One reason is the home run ball. Another is his four-seam fastball, which averages just 91.6 mph and opponents are hitting at a .414 clip. That’s landed Zimmermann in the bottom 20th percentile of total opponent exit velocity, per Statcast, and amplified the importance of his command and secondary pitches.

The home run ball
In a related trend, that hard contact routinely leaves the ballpark. Zimmermann did not allow a home run on Sunday, but it was a rare instance: he’s surrendered at least one homer in nine of his 11 starts, and 12 in 59 2/3 total innings.

“I’ve felt more comfortable after stringing together some decent outings,” Zimmermann said. “I am feeling better each time I take the mound. I really would’ve liked to get one against the Rays today. They are a monkey on my back right now, in a manner of speaking. For the time being, I definitely think I’m settling in well and looking forward to the work in between each outing and getting better.”