Jace Peterson hit a home run in the 10th inning to help the Braves salvage the series finale against the Nationals on Sunday. (Kevin Liles/Getty Images)

Had the Washington Nationals made a list of priorities for Sunday’s game against the Atlanta Braves, it might have read something like this:

One: Get a long start from Gio Gonzalez because the bullpen has been overworked. Two: Use as few pitchers as possible. Three: Clean up the defense after a sloppy series so that those pitchers do not throw unnecessary pitches. Four: Inherent in the other three but almost secondary in the context of this 20-games in 20-days stretch of August angst, win the game. With a 9½ -game lead entering the day, pyrrhic victories can cost more in the long run than a loss here or there.

On Sunday, Gonzalez could not pitch out of the sixth. The Nationals needed three relievers as the game dragged on through a rain delay, then into extra innings. They committed a season-high five errors, most in a game since 2011. They lost, 7-6, when Jace Peterson hit a walk-off home run off Shawn Kelley in the 10th. They finished with three wins in four games in Atlanta, which is not bad for a weekend like this one.

That Manager Dusty Baker needed to call on Kelley at all was a testament to the grind this bullpen has endured lately. Kelley has had two Tommy John surgeries, an injury history that made Baker reluctant to use him two days in a row — let alone four out of five. He hung a slider to Peterson with two outs that ended the game.

Ryan Zimmerman and Chris Heisey celebrate Heisey’s home run as they walk back to the dugout. (John Amis/AP)

“We’re tired. There’s no denying that,” Kelley said. “But we still have to go out and execute.”

Though that poorly executed slider cost the Nationals the game, it did save Baker from having to go deeper into his bullpen. Oliver Perez has been out with back tightness since pitching in Colorado on Wednesday, and is day-to-day, Baker said. He was not available Sunday. Koda Glover and Matt Belisle had pitched two days in a row. Mark Melancon had gone three. Yusmeiro Petit and Blake Treinen already had pitched by the time Kelley entered the game. Had the game gone on, Baker admitted “there wasn’t much of a plan.”

“I know it’s going to be hard to take, but sometimes it’s a blessing in disguise,” Baker said. “because that could have wrecked us for the next week.”

Thanks to a monster home run from Bryce Harper, who is now 12 for 30 (.400) since returning from a stiff neck last weekend, and a two-run shot from Chris Heisey, who was giving Jayson Werth a day off in left, the Nationals had plenty of runs with which to work again Sunday. The game came down to the bullpen, then extra innings, because Gonzalez did not last long enough and their defense let them down.

Gonzalez teetered through 5⅔ innings, allowed three earned runs, and struck out eight. The Nationals, who needed innings from their starter after their bullpen had to cover 161/3 innings in Colorado, used four pitchers Friday, then needed five pitchers Saturday.

Gonzalez fell behind consistently, throwing first pitch strikes to 15 of the 26 batters he faced. He struggled to put hitters away after getting two strikes, which drove his pitch count to 112 before he could finish that sixth.

“I would have to say today, this loss is definitely on me,” Gonzalez said. “I should have gone deeper in the game. After these guys put up four runs in that third inning, I should have gone out there and shut them down with a quick inning.”

Nationals reliever Shawn Kelley exits the field after Jace Peterson’s walk-off home run in the 10th inning. (John Amis/AP)

After Harper’s homer put the Nationals up four, the Braves got three back right away aided by two errors. Shortstop Danny Espinosa, who had an uncharacteristic afternoon, made an error on the first batter of the game. He was then charged with another as the Braves rallied when his throw home bounced away and allowed Nick Markakis, who had just doubled in two runs, to move to third. He scored on an error in center by Trea Turner, who could not get a shallow flyball out of his glove in time to throw home as Markakis tagged up.

Still, the Nationals carried a two-run lead into the eighth. By then, Petit was in his third inning of work. By then, dark clouds had crawled in from left field, bringing with them the third rain delay in the Nationals’ past six games.

Matt Kemp homered to lead off the inning. 6-5. Rain began to fall. Jeff Francoeur singled. Anthony Recker bunted. Petit struggled to pick it up, then rushed his throw to first. Off it went, into the stands, which put the tying run at third and the go-ahead run at second with no one out. Petit intentionally walked Peterson to load the bases. That fifth Nationals error tied a team record, set at Turner Field in 2011.

Then it poured. Umpires stopped play. When it resumed 1 hour 4 minutes later, Treinen got a 6-4-3 double play that scored the tying run, the 15th double play he has induced this season, most in the majors. The game headed to the ninth inning tied, then to extra innings — a fate the Nationals hoped to avoid, but one to which, in some ways, they doomed themselves.

“We didn’t play a good game at all. We played a sloppy game. We’d have been lucky to win that game with five errors,” Baker said. “The game’s not meant to be played 32 outs to 27 outs.”

All of that meant Baker had to call on Kelley, not the ideal man to use four times in five days — though if the Nationals could choose “ideal” these days, Sunday would have gone far differently. Still, they are still 23 games over .500 and comfortably ahead in the National League East, which is the main priority, in the end.