HOUSTON -- Nationals closer Matt Capps thought he had the Astros' Lance Berkman struck out to end the game. So did manager Jim Riggleman. Third baseman Ryan Zimmerman, too.

Instead, third-base umpire Bill Hohn called it a checked swing on Berkman, making the count 2-2, and Berkman lined the next pitch from Capps into left field, scoring two runs to beat the Nationals, 8-7, on Tuesday night at Minute Maid Park.

"I made a good pitch there, and I thought he made a pretty good offering at it," Capps said of the call made by Hohn, who had ejected Astros starter Roy Oswalt in the third inning of Monday's game.

Riggleman didn't like the call at all.

"I say this all the time, to me, the checked swing is one of those calls [where] there's very little consistency," Riggleman said. "Nobody really knows what is and what isn't [a checked swing]. To me, if you checked your swing, that means the pitcher beat the hitter. If there's a gray area, it should be a strike.

"It works that way for both clubs. I'm sure we've gotten away with checked swings that I felt were swings. Tonight it burned us."

"Yeah, he swung," Zimmerman said of Berkman. "I think we should have won that game."

The Nationals thought they had the game won when Ian Desmond and Roger Bernadina delivered back-to-back singles in the top of the ninth, each scoring a run, to put Washington on top, 7-6.

With Capps (0-2) coming out of the bullpen in pursuit of his 18th save, it looked like a lock for the Nationals.

"He's going to pitch [lights-out], we're going to play some defense and we walk away with the 'W,'" Desmond said of the expected outcome.

But Zimmerman, uncharacteristically, made an error on a hard grounder by Pedro Feliz to begin the bottom of the ninth.

"The ball was really hit hard," Riggleman said. "Feliz is a good hitter and he really smoked that ball. Sometimes we take for granted that plays will be made. It was a tough play, and that one got by."

"It was a bad play by me," Zimmerman said. "It happens. I thought it would hop up and it stayed down. It's one I expect myself to make. It's unfortunate to let your team down."

After the Astros sacrificed Feliz to second, pinch-hitter Cory Sullivan drove the ball off the wall in left-center. But Feliz held up, waiting to see if the ball would be caught, and only reached third on the double by Sullivan.

The Nationals intentionally walked Michael Bourn to load the bases.

"We had a good plan there, to walk Bourn and set up the double play, or at least the forceout at the plate," Capps said.

Jeff Keppinger did exactly the latter, grounding into a second-to-home forceout, the bases remaining loaded with two outs.

Up stepped Berkman.

"If I'm perfect, I don't even have to worry about it," Capps said of the checked swing. "I don't even have to face Berkman in that situation. I tried to bear down, and execute, and felt like I did. It was nice piece of hitting on the 2-2 pitch after that.

"It's frustrating, but you can't put it in an umpire's hands. Those guys are pretty good. Those guys are on national television. They don't want to get anything wrong. It's hard to say it was one way or another way. I made a good pitch there.

"I was pretty shocked [Hohn called no swing]. But he's got a much better view over there than I do. I'll take his word for it."

Washington starter Craig Stammen barely got out of the first inning. The first five Houston hitters reached base and the Astros scored three runs in the inning.

"It was just hard to get out of that first inning," said Stammen, who recovered to last five innings, allowing five runs over his outing. "[The pitches] were up, over the plate, easy to hit. It's tough when you're the reason we got behind. Lucky for me, I didn't' get the loss."

The Astros led, 4-0, after three innings, but the Nationals tied it in the top of the fifth, scoring three unearned runs on two Houston errors.

Berkman made one of them, throwing home with the bases loaded to force a runner at the plate. But the ball hit the dirt, bounced away from Houston catcher Kevin Cash, and two runs scored.

"I felt like we shouldn't have even been in that position, because I made a bad throw home and that ended up costing us three runs," Berkman said. "To be able to atone for that late in the game, that helps you sleep."

Washington closed the gap to 6-5 in the eighth when pinch-hitter Willie Harris was hit by a pitch to score a run.

Nyjer Morgan started the Nationals' rally in the ninth with an infield single, and after Zimmerman and Adam Dunn walked, Desmond and Bernadina delivered in the clutch.

"I'm just really proud of the way the ballclub, the way we came back," concluded Riggleman. "We're down, 4-0, and [Houston starter Brett] Myers is pitching pretty good."

"We did battle back twice," Desmond said. "That says something about this ballclub. It's a loss tonight, but maybe a small victory in the end."