WASHINGTON—The Orioles’ fifth straight loss and their 12^th in the last 14 games wasn’t the fault of the offense. In the previous two losses, the Orioles had managed just three runs on six hits. They scored nine runs and twice had five-run leads, but their pitching undermined them in a 12-9 loss to the Washington Nationals before 15,440 at Nationals Park on Saturday.

Ryan Mountcastle’s first grand-slam and his fourth home run helped give Bruce Zimmermann a 5-0 lead before he took the mound, but he made it through just three innings.

Zimmermann, who threw 5 2/3 strong innings in relief of opener Adam Plutko last Sunday against the Yankees, threw 82 pitches in just three innings.

“My stuff was crisp against the Yankees,” Zimmermann said. “I thought it was crisp today. It was just the fact that I ended up going into those deep innings. I was up to 70 pitches in the third. I’m not going to lie. I did get a little tired there in the third inning.”

He rejected the idea that he’d be better as a reliever.

“I still believe very strongly that I’m a starter,” Zimmermann said. “I still think that’s my best opportunity here to give the team what I’m best at. It’s baseball. It’s the big leagues. Those innings, it can be a toll on the arm to go into those pitch counts.

“I believe I can be an asset as a starting rotation guy. I can pick up innings. If it’s needed, I’ll be in the bullpen, but as of right now, I still believe I’m definitely a starter on this team.”

Plutko (1-1) allowed four runs in the fourth inning, including a three-run home run by Ryan Zimmerman. Bruce Zimmermann gave up Josh Harrison’s grand-slam in the third, which erased the Orioles’ big lead.

Before his inning as an opener, where he allowed four runs, Plutko had a 1.27 ERA. On Wednesday, Plutko gave up two runs to the Tampa Bay Rays while retiring just one batter. After the four runs in two innings, the ERA is 4.74.

“You can dwell on negatives all day long, but in baseball, this game’s hard enough, so let’s look for some positives,” Plutko said.

Plutko cited his scoreless fifth inning, Cole Sulser’s scoreless seventh and Shawn Armstrong’s scoreless eighth.

“I know what my line was, and I know what my first inning was,” Plutko said. “What’s the point of beating up myself on that? That seems pretty pointless. What’s the point of dwelling on a lot of us maybe struggling for a hot minute? Let’s build on the positive.”

The Orioles (17-28) had 12 hits. In his second game since returning from more than a month on the injured list because of a sprained left ankle, Anthony Santander had three hits, including his third home run.

Tanner Scott allowed three runs, including an unearned run that scored on third baseman Maikel Franco’s error in the sixth when Washington took a 12-7 lead.

Pat Valaika had a two-run double in the eighth to cut the Nationals’ lead to 12-9.

Manager Brandon Hyde said that the team would consider making changes to the pitching staff before Sunday’s game.

“We did some nice things offensively,” he said. “We’re just having a tough time on the mound … Once again, we’re running on fumes, pitching-wise.”

Daniel Hudson (3-0) allowed a single to Cedric Mullins in the eighth but, with runners on first and third, retired Freddy Galvis on a pop to short and struck out Trey Mancini.

Brad Hand polished off the Orioles in the ninth for his sixth save.

Hyde is concerned about the string of losses.

“You want your guys to feel good,” Hyde said. “I do worry about that. It’s been a couple of tough years, and we’re not winning these games here the last couple of weeks. That’s tough. It’s not easy. It’s tough to lose in the big leagues. You want guys to feel success.”

Harvey rehab appearance: Hunter Harvey, who hasn’t pitched this season because of a strained left oblique, will make his first rehab appearance for Triple-A Norfolk on Sunday.

The right-hander will make some rehab appearances until he’s eligible to come off the 60-day injured list during the Orioles’ next homestand that begins on May 31st, Hyde said.

“We’ve scheduled out his outings for the next eight, nine days,” Hyde said. “Then, hopefully, he’s ready to join us.”

Minor Matters: Right-hander Mike Baumann, who has been slowed by a forearm injury last fall, is moving up to Double-A Bowie from Low-A Delmarva. Baumann threw five hitless innings in two starts for the Shorebirds, striking out six and walking three. … Kyle Bradish, who was one of the four pitchers Orioles obtained in the December 2019 trade for Dylan Bundy, is being promoted from Bowie to Triple-A Norfolk. Bradish was 1-0 in three starts and didn’t allow a run in 13 2/3 innings. He gave up seven hits, struck out 26 and walked five. … The Tides will allow full-capacity crowds at Harbor Park beginning on May 28th.

Coming up: Matt Harvey (3-4, 5.93 ERA) will face Patrick Corbin (2-3, 6.10) on Sunday afternoon at 1:05.