The 24-year-old lefthander allowed just two hits over six innings to pick up his first major league win as the Pirates dropped the Braves 2-1 to end Atlanta's shot at winning the National League East.
The Braves, at least, are still heading to the playoffs as a wild card. Those prospects are long gone for Pittsburgh, which saw its best season in 20 years unfold during a 7-21 September.
Locke has been along for the ride. He came in winless in his big league career and — even worse — the Pirates hadn't won a game in which he appeared in any capacity this season.
That ended on a night when he kept surging Atlanta at bay, striking out six and walking five.
"All in all it feels good to get it out of the way so that people don't talk about it anymore so that if you lose 150 more, then I'll still have the win," Locke said with a laugh.
Starling Marte hit his sixth home run of the season and scored twice for Pittsburgh while Jared Hughes worked the ninth for his second save.
"It just feels good to win, after everything this team has been through this year, especially this last little while," Locke said.
Paul Maholm (13-11) gave up two runs in seven innings while losing to his former team for the first time, striking out eight and walking three.
The Braves came in hoping to finally track down the Washington Nationals. They came to Pittsburgh with an 8-2 record in their last 10 games to draw within 3 games of first place.
Their September surge put to rest the memories of their nightmarish collapse last fall when they blew a huge cushion over the season's final month and missed the playoffs entirely.
Still, Atlanta's chance of winning its first division crown since 2005 ended when it couldn't muster much offense against a team in the midst of its own personal nightmare.
"It's something we shoot for, the division," Atlanta manager Fredi Gonzalez said. "We didn't get it, but we've got the wild card game and you know there's been many, many teams that go through the wild card to win the World Series."
Locke has spent the last month auditioning for a spot in Pittsburgh's rotation next spring, his frustrating results coinciding with the team's freefall through the standings.
Needing to put something together to prove he can compete for a spot in the rotation next spring, Locke settled in quickly. Atlanta's only run came on Jason Heyward's RBI single in the third but the Braves left the bases loaded when Freddie Freeman grounded out to end the inning.
"I think there was a couple things out there tonight that really helped his growth," said Pittsburgh manager Clint Hurdle. "Getting through the third and only giving up one run was one of them."
Atlanta's lead didn't last long. Marte tripled to lead off the third and scored Chase d'Arnaud's grounder to second.
Marte, part of a young core the Pirates plan to build around, led off the fifth with a drive over the 399-foot sign in center field to give Pittsburgh the lead and the Pirates spent the last four innings relishing the chance to put a dent in Atlanta's postseason plans.
The Braves went quietly until the ninth, when Freeman reached on an error with one out. Reed Johnson lined to left and Brian McCann grounded out to Hughes that led to cheers in two cities about 250 miles apart.
"It's special, this whole night and day has been special," Locke said. "It feels good to go out there and compete and compete and compete. It just feels good to finish out on a good note."
NOTES: The Braves scratched 2B Dan Uggla about an hour before the game as a precautionary measure due to swelling in the knuckle on his right index finger. Uggla injured the hand when the Braves celebrated clinching a playoff spot last week. Martin Prado started in Uggla's place, with Johnson replacing Prado in the outfield ... Atlanta manager Fredi Gonzalez said there are no plans to change the pitching rotation through the final two games of the season even with Atlanta locked into the wild card ... The series continues on Tuesday, with Atlanta's Tommy Hanson (13-9, 4.38) facing Pittsburgh's Kevin Correia (11-11, 4.33) ... The Pirates honored Atlanta 3B Chipper Jones before the game by giving him a specially branded base that will be used during the series and donating $5,000 to the Cystic Fibrosis Foundation.