"The bicep is fine," Strasburg said. "Starting out, I threw a lot of pitches early and then we put up a lot of runs. I got a little tired. [The bicep] got a little tight. It's nothing different than any other outing. It's probably gonna be like this for the rest of the year. It's all part of coming back from Tommy John [surgery]. It's something I have to be smart about."
Washington (24-17) snapped a three-game losing streak, which had tied a season high. The Nationals now embark on a nine-game road trip against division foes Philadelphia, Atlanta and Miami.
Strasburg allowed three runs (one earned) on four hits with eight strikeouts and one walk over five innings. He improved to 4-1 with a 2.21 ERA on the season. After Jesus Flores gave the Nationals their first lead of the series with a solo home run in the fourth, Strasburg followed with a towering shot to left-center to go back-to-back and make it a 5-3 game.
"Straus is not a complainer," Johnson said. "If he had told me there was tightness after the first inning, I would have hooked him then to be on the safe side. I would have liked to have know he had a little discomfort. The bicep being tight probably scares me the least."
Orioles' lefty Wei-Yin Chen suffered his first big league loss, allowing a season-high six runs on eight hits with five strikeouts and three walks over 4 1/3 innings.
The Nationals, who dropped their first home series of the season, are nonetheless off to their best start since arriving in D.C., and remain in second place behind the Braves.
After the Orioles took a 1-0 lead in the first on an RBI single by Nick Markakis, a couple of defensive miscues allowed them to increase the margin two innings later. Wilson Betemit reached second base after Bryce Harper dropped a routine fly ball to center field. Betemit then scored on a groundout by Robert Andino.
A passed ball later in the frame set up an RBI single by Xavier Avery that gave the Orioles a 3-0 lead. Neither of the runs were charged to Strasburg.
"We scored three runs and could have scored a lot more," Orioles manager Buck Showalter said. "I think it was more that we made a lot of mistakes with our breaking ball today. We dialed it up early and had some good at-bats and looked forward to the challenge of facing a good-looking young pitcher."
Strasburg boosted the offense by leading off the third with a single. Danny Espinosa followed with a double and Harper atoned for his error by cracking a two-run triple to cut Baltimore's lead to 3-2. Ian Desmond tied the game on a fielder's choice when he barely beat out a throw to first base that would have finalized a double play.
"I was just trying to go for that ball. I had a good read on it, but I just dropped it," Harper said about the miscue. "To be able to get something going was huge. It was a pretty big win today."
Strasburg's long ball was the first home run by a Nationals pitcher this season. Desmond had an RBI single in the fifth and Espinosa delivered another staggering blow with a two-run homer in the eighth.
"It was a lot of excitement out there," Espinosa said. "There was more energy on the field. It was a lot of fun. When you're playing for first place in your division, it's more exciting. You're not trying to pick up fourth place or anything like that. It's early in the season, but if we continue to play good ball, we're gonna be right there at the top."