The Nationals were down, 5-4, when they made their comeback. With right-hander Chris Ray on the mound, pinch-hitter Anderson Hernandez and center fielder Willie Harris started the inning off with singles. After both runners advanced a base on Cristian Guzman's sacrifice bunt, Ryan Zimmerman was intentionally walked to load the bases. That brought Dunn to the plate.
"I'm always surprised when I get walked intentionally," Zimmerman said. "Adam has been swinging the bat well the last couple of days."
Ray left the game in favor of left-hander Jamie Walker. Orioles manager Dave Trembley was playing the percentages, and the left-handed-hitting Dunn took notice of it.
"I could see why they would do it, but I don't like it," Dunn said.
The strategy didn't work out for the Orioles, as Dunn came to the plate and hit a 2-2 pitch into the left-field bullpen for a grand slam.
"I got two strikes. With a pitcher like that with so many pitches, I was trying not to pull off and hit into a double play," Dunn said.
It was Dunn's second homer of the game and the 10th grand slam of his career. He ended up with six RBIs for the day.
"I just made the one bad pitch. Actually, I made two," Walker said. "That hanging slider that he fouled back was probably the pitch I thought he'd hit out. We were trying to go in right there -- 2-2 count -- and my ball just cut and ran right back over the outer third [of the plate], right in his homer-zone. He did what he's supposed to do. I made one bad pitch, and it cost us the game. That's the life of a reliever."
After the game, Nationals manager Manny Acta talked about how much Dunn has made a difference in the lineup. For example, if Dunn were not on the roster, Guzman would not have bunted in that inning, and Zimmerman would not have walked intentionally.
"Adam showed how much we needed him over here. You could tell the difference when we don't mind bunting Guzman," Acta said. "But it's a totally different story when you have a guy like Dunn behind Zimmerman."
The Nationals' bullpen, which has been the club's Achilles' heel all season, did the job on Sunday. It pitched a combined three innings without giving up a run. Ron Villone picked up the win, while Joel Hanrahan saved his fifth game of the season.
The Nationals ended their homestand with a 2-8 record. They will now travel to New York and play a three-game series against the Mets starting Monday night.
"It's all about momentum," Harris said. "We are going to score runs. If our pitchers keep us right there, we are going to have a shot to beat a lot of teams. There are a lot of teams that don't want to play us, even though we have the worst record in the game."
Right-hander Shairon Martis, who remains undefeated, started for the Nationals and didn't have his best outing, lasting six-plus innings and giving up five runs. He had problems with his command throughout the game. In fact, Martis went into the fifth inning having thrown only 50 percent of his pitches for strikes.
"I didn't have the confidence that I used to have. I wasn't focused all the time. Maybe I was rushing. I was trying to be too fine," Martis said.
By the third inning, Martis was behind 2-0 because of a two-run triple by Nick Markakis.
Baltimore added to their lead in the fifth, when Aubrey Huff drove in Adam Jones with a single.
By the sixth inning, however, Washington had a 4-3 lead. Dunn highlighted the scoring with a two-run homer off right-hander Brad Bergesen.
Martis lost the lead when he gave up a two-run homer to Jones in the seventh. Martis had a feeling, however, that Washington's offense would come back and win the game.
"With this offense, if it's close, we still have a chance, and that's what happened," Martis said.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.