WASHINGTON -- Wei-Yin Chen wasn't fooling anyone with his breaking ball, least of all Stephen Strasburg.
Chen gave up a home run to Washington's starting pitcher and didn't make it out of the fifth inning in Baltimore's 9-3 loss to the Nationals on Sunday.
The defeat ended the Orioles' five-game winning streak and nine-game road run. Baltimore scored the game's first three runs but got only two hits after the second inning – both in the ninth.
Chen (4-1) yielded six runs and eight hits in 4 1-3 innings and absorbed his first major league loss. The Taiwan native was vying to become the first Baltimore starter to begin his Orioles career with five straight wins since Jimmy Key in 1997.
"This is baseball. Sometimes you have a good day, sometimes you have a bad day," Chen said through a translator. "Definitely, I had a terrible start today."
The lowlight was Strasburg's first major league home run. The hard-throwing Strasburg (4-1) is better known for his pitching, but he singled and scored in the third inning before hitting an 0-2 pitch over the left-field wall and into the Washington bullpen in the fourth.
"I just realized pitchers can hit here, and I made a big mistake here and threw a bad pitch," Chen said.
Orioles manager Buck Showalter said, "He hung a breaking ball. That's what most people do who are big and strong like their pitcher is. I bet you could find a few pitchers who would hit that pitch out of the ballpark. He put a good swing on it and it carried out."
Chen's problems extended beyond his dealings with Strasburg.
"He made a lot of mistakes with his breaking ball today," Showalter said. "That was pretty much the difference."
Despite the loss, the Orioles went 4-1 on a swing through Kansas City and Washington and remain atop the AL East.
"We're playing really well on the road," first baseman Chris Davis said. "Obviously, we would have loved to sweep these guys, but you'll take a series win anytime on the road. They're a good team. They've played well so far."
After dusting off his home run trot and returning to the dugout, Strasburg responded to a curtain call by waving to the crowd of 41,918.
"Shocking, that's for sure," Strasburg said. "I feel like in (batting practice) I have to swing a lot harder to hit it out. I just somehow ran into one."
Strasburg had five hits in 40 big league at-bats before Sunday. On the mound, he allowed three runs, one earned, four hits and a walk in his first career appearance against Baltimore. He retired the last 10 batters he faced.
Since returning from elbow ligament replacement surgery last September, Strasburg is 5-2 with a 1.99 ERA in 14 starts.
Danny Espinosa also homered, and Bryce Harper drove in two runs and scored three for the Nationals.
Baltimore went up 1-0 in the first when Xavier Avery walked, advanced on a fly ball and scored on a single by Nick Markakis.
The Orioles added a pair of unearned runs in the second after Harper drifted from center to left field to chase down a wind-blown fly ball, then dropped it. Robert Andino drove in a run with a groundout and Avery added an RBI single before Strasburg struck out J.J. Hardy with two outs and runners on second and third.
Harper made amends in a three-run third. Strasburg singled, Espinosa doubled and Harper hit a liner to right that a diving Markakis gloved but lost when he hit the ground. The triple scored two runs, and Harper scored on a groundout by Ian Desmond.
Flores gave Washington a 4-3 lead with his first homer since Aug. 18, and that only served as a prelude to Strasburg's clout.
Desmond chased Chen with an RBI single in the fifth, and Espinosa homered with a runner on during a three-run eighth.
NOTES: Orioles C Matt Wieters, who had the day off after a night game, will have to wait until Monday to try to snap an 0-for-18 slump. ... Tommy Hunter (2-2) takes the mound for Baltimore on Monday night in the opener of a three-game series against visiting Boston. ... Gio Gonzalez vies for his sixth win when the Nationals open a nine-game road trip Monday in Philadelphia. ... Avery got his first major league stolen base. ... Washington Capitals forward Jason Chimera fired a strike with the ceremonial first pitch.