A fastball down the middle.
And he got one.
"I was just going to concentrate on one pitch, and he threw it right there," Pena said, "and good thing I didn't miss."
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"We know the game's not over until we're back in the clubhouse," said Chris Johnson, whose seventh-inning homer off Nationals starter Ross Detwiler began Atlanta's rally from a four-run deficit. "I think there's a deep part of everybody that thinks we are going to come back every time it happens, so it's a good feeling."
Pena, cut by the New York Yankees last September, reached on a bunt as a pinch hitter in the eighth, when the Braves scored once. They added two in the ninth and another two in the 10th against the Nationals' bullpen.
Detwiler has two no-decisions despite a 0.69 ERA, because relievers twice gave up leads.
"We need to do better," said Tyler Clippard, who replaced Detwiler to begin the eighth. "Ross pitched a [terrific] game. It hurts. It hurts, obviously, for the club to get the loss. But it hurts for him. ... To have your starter do what he did and not get the win for him is very, very disappointing for us as a group."
With one out in the 10th, Stammen (2-1) walked Dan Uggla. After a flyout, Pena hit his first homer of the season to right.
The Braves, a major league-leading 9-1, handed Washington its first loss in seven home games.
Atlanta tied the game in the ninth, when Washington third baseman Ryan Zimmerman's throwing error contributed to reliever Drew Storen blowing a save. It was Storen's first save chance since giving away a ninth-inning lead against the St. Louis Cardinals in Game 5 of an NL Division Series last season; Washington led that game 6-0 early and 7-5 entering the ninth.
On Friday, Nationals manager Davey Johnson wanted to stay away from new closer Rafael Soriano, who had pitched each of the previous three days, earning three saves during a sweep of the Chicago White Sox.
In the eighth, Clippard got two quick outs before everything started to unravel.
He went walk, single, walk, walk - with that last pass to B.J. Upton forcing in a run to make it 4-2.
"The execution wasn't there. My changeup was nonexistent tonight," Clippard said. "I wasn't able to put that where I want to, and that hasn't happened in a long time."
On came Storen. He got the third out of the eighth on a fly ball to the warning track in center by 26-year-old rookie Evan Gattis.
Then, in the ninth, consecutive singles off Storen put two runners on, and a sacrifice bunt pushed them to second and third. With two outs, Storen walked Jason Heyward to load the bases for Justin Upton, B.J.'s brother.
Justin Upton hit a hard shot to Zimmerman, who tried to throw to second for a forceout that would have ended the game. But Zimmerman's throw was wide of the bag and sailed into right field. Justin Upton was credited with a single and one RBI, while the second run that scored on the play was unearned because of Zimmerman's throwing error. That made it 4-all.
"Tough play. I think, obviously, first base is out of the question. I'm not going to beat the guy to third. I thought if I turn and make a perfect throw, I had a chance to get the guy bang-bang at second," Zimmerman explained.
"We definitely need to learn from our mistakes," he added. "It's the same thing that kind of got us last year, and why we didn't maybe move on, because we couldn't close games out both pitching and defense-wise."
Braves starter Julio Teheran gave up four runs and six hits in six innings, including Bryce Harper's fifth homer, a two-run shot in the first. Washington added RBI singles by Denard Span and Jayson Werth in the second.
But the Nationals didn't score again.
"We just kept plugging away, plugging away, scoring some runs," Braves manager Fredi Gonzalez said, "and set it up for Ramiro."
- In the sixth, umpires reviewed Justin Upton's hit off the top of the wall to see if it was a homer, but ruled it was a double. Upton stayed at second because Detwiler struck out Gattis.
- Gattis played first base for the first time since Class A in 2011. He mostly looked fine, with one bad-looking play in the fifth, when Harper lofted a high popup in foul territory that Gattis lingered under but misjudged, the ball dropping to the ground. Harper eventually walked but was stranded at second.
- RHP Luis Ayala pitched a hitless seventh in his Braves debut.
- Zimmerman played in his 1,000th game with the Nationals.