WASHINGTON -- Josh Willingham has enough experience at game-winning celebrations to have had an important lesson beaten into his head.
"I've learned not to take your helmet off," Willingham said with a smile. "You get hit pretty hard."
"He's just a professional hitter. He's the ultimate pro," Nationals manager Jim Riggleman said. "You don't see Josh make too many mistakes on the baseball field. He's solid as a rock and will give you a good at-bat every time out."
Orioles closer Alfredo Simon left in the 10th after injuring his left hamstring while running to first base to cover on a grounder for the first out. Simon was replaced by Cla Meredith (0-2), who allowed Willingham's eighth homer, a drive to left-center on a 2-1 fastball.
"It was a pitch out over the plate, and I wasn't trying to hit a home run," Willingham said. "I was just trying to hit it hard. It got up in the air and went out."
Because he entered the game following Simon's injury, Meredith had as much time as he needed to warm up. But Willingham made it a short work day for the sidearming reliever.
"I want to step up and be better in that situation -- if anything, just for them, the way they played today," Meredith said. "I just got to be better than that."
The severity of Simon's injury wasn't immediately known. The right-hander, a starter in the minors, was summoned from Triple-A on April 27 after Baltimore lost closer Michael Gonzalez to a left shoulder strain and his replacement, Jim Johnson, was inconsistent.
The Orioles were short a man in an overtaxed bullpen because right-hander Koji Uehara was unavailable with an elbow problem. Uehara was examined by a team doctor before the game, but no determination has been made whether he will go on the disabled list.
"It takes its toll on your bullpen," Baltimore manager Dave Trembley said. "You're doing everything you possibly can to try to win the game, and I thought we did."
Baltimore tied it in the ninth when Capps was unable to protect a 3-1 lead for his first blown save in 17 chances.
With one out, Capps allowed an infield single to Luke Scott and a double by Adam Jones, who extended his hitting steak to 10 games. Matt Wieters hit an RBI groundout before Julio Lugo's game-tying RBI single to right.
"I've thrown a lot worse and had three-up, three-down innings," Capps said. "That's just the way it goes sometimes. Lugo battled me a little bit. I threw a pitch that was down in the zone, but it ran back over the middle of the plate. It was just one of those days for me."
It was Washington's first win in four extra-inning games this year. The Nationals have won seven games in their final at-bat.
The Orioles were deprived of their first road series win of the season.
Doug Slaten (2-0) pitched a perfect 10th inning.
Washington loaded the bases when Nyjer Morgan singled, Cristian Guzman executed a successful drag bunt and Willingham was hit on the right shoulder before Bernadina hit a two-out triple to center. Jones couldn't snag Bernadina's fly ball as he crashed into the wall.
Baltimore starter Kevin Millwood allowed three runs on eight hits in 6 1/3 innings, walking one and striking out eight. John Lannan, the Nationals' starter, yielded a run on two hits in 5 1/3 innings, walking three and striking out two.
The Orioles have scored 30 runs in Millwood's 10 starts, but only 17 when he was in the game. ... The Nationals improved to 14-13 against the Orioles in interleague play. The teams meet for a three-game series in Baltimore from June 25-27. ... Baltimore last won a road series against the New York Yankees Sept. 11-13, 2009. ... Before the game, the Nationals recalled OF Justin Maxwell from Triple-A Syracuse. ... Washington rookie RHP Drew Storen got a hit in his first major league at-bat, a sixth-inning single to left. Storen said it was his first at-bat since high school.