Nationals 9, Orioles 3: Stephen Strasburg pitched five solid innings and helped himself with a solo homer as host Washington avoided a sweep in its three-game Beltway series against Baltimore.

Bryce Harper added a two-run triple and Jesus Flores hit a solo homer for the Nationals, who had dropped one-run decisions in each of the first two games.

The Orioles jumped on top again Sunday, getting an RBI single from Nick Markakis in the first inning and taking advantage of Harper’s error to push two unearned runs across in the second.

Strasburg (4-1) settled down after that, retiring the final nine hitters he faced and piling up eight strikeouts while walking one and surrendering four hits.

Harper atoned for his miscue in the third, following a Strasburg single and Danny Espinosa double with a triple to right that popped in and out of Markakis’ glove as he dove for it. Ian Desmond knotted it at 3-3 on an RBI groundout.

Strasburg put himself on top, 4-3, in the fourth, driving an 0-2 pitch from Wei-Yin Chen just over the wall in left-center for his first career homer.

Chen (4-1) suffered his first major-league loss, allowing more than three runs for the first time in his career. The Japanese left-hander was charged with six runs on eight hits in 4 1/3 innings.

GAME NOTEBOOK: Espinosa tacked on a two-run homer in the eighth inning, his fourth. He came into the contest slugging a paltry .307 after posting a .414 mark and 21 homers in 2011. … Baltimore rookie Xavier Avery drove in a run and scored. He has four multi-hit games in the first eight games of his career. … Orioles slugger Adam Jones went 1-for-4 to extend his hitting streak to 12 games.