BALTIMORE -- The Orioles had little room for error Sunday against the Nationals.
Vladimir Guerrero struck a go-ahead home run in the seventh and a precision throw from catcher Matt Wieters nabbed Brian Bixler -- who represented the tying run -- on an attempted steal of second to close out the Orioles win.
The pair of plays, backed by a solid start from Chris Tillman, secured the Orioles' 2-1 win on Sunday, as well as the Battle of the Beltways series.
With one swing of the bat, free-agent acquisition Guerrero gave Baltimore the offense it sorely needed, as the slugger sent an offering from Nationals starter Jordan Zimmermann into the left-field seats for a two-run homer that put the O's on top.
"[Sunday was] a good example of what he can bring for us, just his presence as much as anything," manager Buck Showalter said. "A lot of times he walks through the door like he's playing his first game of Little League, the zest that he has for the game and the day to day things that go on for a baseball team for seven or eight months. You look at a guy like him and you realize how much he's going to miss it when he doesn't play. I've been around him a while now, and I've never seen him have a bad day."
The Orioles only had one hit entering the seventh inning against Zimmermann, who retired 13 straight batters heading into the frame. But, the Baltimore bats put the cold start behind them and made sure the second and third hits counted.
Right fielder Nick Markakis hit a leadoff single to right, putting the tying run on base for Guerrero, who entered Sunday's game hitting .371 in May.
On an 0-2 count, Guerrero belted a Zimmermann curveball 365 feet to left, landing in the first row of the bleachers.
"The pitch just hung up a little bit," Zimmermann said. "He is a tough hitter to pitch to. You have to mix it up. I threw balls in the dirt. I threw them high. You have to pretty much mix it up and hope for the best."
The two-run shot gave the Orioles a fragile 2-1 lead. It also marked the 11th time in the last 12 games that Guerrero reached base safely.
"I was looking for a good pitch to hit and just to make contact and not for a home run," Guerrero said through interpreter Rudy Arias. "But I hit it out."
Wieters said Guerrero's advantages extend beyond the plate.
"He's a Hall of Famer for a reason," Wieters said. "He's a guy that can get to any pitch at any time. And more than anything, just to see the way he plays the game is good for all the guys in the clubhouse."
While Wieters had praise for the player who gave the O's their only runs, the Baltimore catcher was the key to closing out the victory.
Orioles closer Kevin Gregg, who was on for the save opportunity in the ninth, was faced with a tension-filled at-bat by Washington center fielder Roger Bernadina. Gregg had already pitched into full counts twice in the frame, grounding out one batter and walking the other.
With the count full against Bernadina and pinch-runner Bixler leading off first, Gregg delivered a called strike for the second out. As the ball cradled in Wieters' glove, the 25-year-old burst out of his stance and fired a pinpoint throw to shortstop J.J. Hardy as Bixler slid into second. The tag was in time.
"I knew [Bixler] would be running," Gregg said. "They didn't put him over there just to stand over there. I'll take my chances anyone running on Wiets."
The throwout was Wieters' second of the game, giving him 14 on the season -- good for fourth-most in the Major Leagues.
"[Bernadina] took the pitch, so that makes it a little bit easier, you don't have the swing getting in front of you," Wieters said. "But if you know your pitcher can throw a lot of pitches for strikes, a 3-2 breaking ball -- if he puts it in for a strike -- you know you are going to have a pretty good chance to throw the guy out."
However, Wieters was only able to be in the position to make the clutch final out thanks to Tillman and the bullpen, which had allowed a run in 20 of the last 21 games.
Tillman gave up just one earned run on six hits, but only lasted five innings due to a pitch count of 97. While it took the Orioles seven innings to figure out Zimmermann, Tillman gave the Nationals opportunities to score early and often.
Tillman said he was frustrated he had to make an early exit from the game.
"Those guys fouled off pitches and fouled off pitches, and you do everything you can to get them to put it in play," he said. "But at the same time, if you're falling behind 2-0, 3-0, it's not easy pitching like that. Guys get to select the pitches that they want to hit. I think I made it tough on myself sometimes, but other than that, guys seemed to do a pretty good job of seeing a lot of pitches."
In the top of the first, a call from home-plate umpire Todd Tichenor prevented Bernadina from advancing to first on a bunt. Just as it had appeared Bernadina had safely reached first, Tichenor made the ruling that he had stepped out of the batter's box on the bunt, and was therefore out. As Tichenor made his call, Nationals manager Jim Riggleman sprang from the dugout, argued his case to the umpire, and was thrown out two pitches into the game.
Ian Desmond followed the contested call with a double. Had Bernadina been ruled safe, Tillman would have found himself in some early trouble.
Again, the right-hander was able to wiggle out of a jam, this time in the third. With runners at second and third and one out, Tillman struck out Desmond swinging and Laynce Nix looking to escape the inning unscathed.
"That cutter finally came around today," Tillman said. "I made some pretty good pitches with it, got some big outs with that. I'll probably take what I had from this start hopefully into the bullpen, and then the next start."
It appeared that Tillman would once again pitch himself out of a difficult situation in the fourth, but the Nationals capitalized on the opportunity.
With the bases loaded and two outs, Tillman got ahead of Washington catcher Alex Cora, 0-2. However, Cora struck a liner that ricocheted off Tillman and was mishandled by Mark Reynolds, allowing Werth to score, putting the O's in a 1-0 hole.
However, four members of the Orioles bullpen pulled together four shutout innings to preserve the win, with reliever Jim Johnson notching the win and Gregg recording his eighth save.
The victory give Baltimore two straight wins after dropping their first three in an eight-game homestand.
"Anytime you can win a 2-1 game like that -- Till did a good job on the mound, the bullpen held it together and Vladdy coming up with the big home run -- you can draw it up, that's pretty big momentum for us," Gregg said.
Avi Zaleon is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.