BALTIMORE - Jonathan Schoop stood in front of his locker after Friday night's game wearing a huge smile, and it wasn't difficult to figure out why.

Schoop hit a solo homer with two outs in the bottom of the ninth inning off right-hander Tanner Roark to give the Baltimore Orioles a walk-off 3-2 victory over the Washington Nationals on Friday night.

The Orioles second baseman returned last Sunday after missing over two months with a sprained knee but is quickly contributing both on offense and defense. He made some tough defensive plays again at second, helping Baltimore turn a pair of double plays, but it was what Schoop did in the ninth that made the difference.

The second-year player lined a homer to left field on a 2-2 pitch from Roark (4-4) for the first walk-off homer of his young career. He got the traditional post-game pie in the face from center fielder Adam Jones and wore that huge grin afterward.

"It's exciting, really exciting," said Schoop, who finished 2-for-4. "I was looking for a pitch I can drive, and I got lucky enough to put a barrel on it, and the ball went out."

Schoop now has two homers in the five games since he returned from the disabled list and is rounding into the form he showed last year.

Roark came on in the ninth and struck out the first two batters before running into trouble with Schoop.

The right-hander said he thought the 2-2 pitch might've been a bit too high.

"He got some good wood on it, and it got out of here," Roark said. "That's really basically what happened. I just checked it out. I thought it was a good pitch."

Orioles manager Buck Showalter also was impressed by how Schoop helped on offense and defense. Showalter said there were at least four defensive plays that Schoop made which he liked

"And I'm probably missing one," Showalter said. "Jon impacted the game on a lot of fronts tonight."

The Orioles (44-42) snapped a three-game losing streak and won for the first time in 2015 when trailing after seven innings. They were 0-36 before that.

Orioles closer Zach Britton (1-0) picked up the victory after a scoreless ninth. The game between the two Beltway rivals who are about 40 miles apart drew the season's best crowd at Camden Yards - 46,289.

The Nationals (46-39) scored twice in the fifth to take a 2-1 lead, which they held until Baltimore tied it in the eighth.

Orioles pinch-hitter Chris Parmelee led off the eighth with an infield single against right-hander Casey Janssen. Two batters later, Parmelee scored from first when catcher Matt Wieters doubled on the first pitch from left-hander Matt Thornton.

The Orioles took a 1-0 lead when center fielder Adam Jones homered to start the bottom of the fourth. He crushed the first pitch from Nationals starter Gio Gonzalez halfway up the lower deck in left field.

Washington answered in the top of the fifth. Baltimore starter Chris Tillman gave up back-to-back singles to start the inning and nearly escaped trouble when catcher Jose Lobaton grounded into a double play.

Left fielder Clint Robinson made it to third on the double play and he scored when first baseman Tyler Moore lined his two-out double to right. Center fielder Michael A. Taylor followed with a single to left that scored Moore for a 2-1 lead.

The Nationals still missed some good scoring chances midway in the game. They got five hits in the fifth but just the two runs. In the sixth, Washington left runners at second and third.

"We had some opportunities with guys out there, but still we're in the game, and one swing of the bat either way can make the difference," Nationals manager Matt Williams said. "Tonight it was for them."

NOTES: Orioles manager Buck Showalter confirmed before Friday's game that RHP Miguel Gonzalez and LHP Wei-Yin Chen will start the final two games of the series against the Nationals. ... Showalter also said the Orioles probably won't make roster moves like sending a veteran starting pitcher down (as they did with Chen earlier) to bring up some extra help. The roster that plays Friday should be the one that goes through the series. ... RHP Jordan Zimmermann was placed on the paternity list before Friday's game as his wife gave birth to a baby girl early Friday morning. But Washington manager Matt Williams said Zimmermann will return to start the second game of the series on Saturday. Williams won't yet commit to a starter for Sunday. ... CF Denard Span was placed on the 15-day disabled list, retroactive to July 7 (back tightness), but results of his MRI exam and a visit to a specialist found no structural damage. The Nationals are hoping he'll be back when the DL stint ends.