After Friday's 11-inning demoralizing defeat, the Nationals promptly lost the opener of Saturday's doubleheader and the prized rookie to an injured ankle. Without Harper in the starting lineup for the nightcap, Washington fell behind by two runs in the first inning.
But the 19-year-old returned to single and score as a pinch-hitter, Roger Bernadina had a tiebreaking hit in the seventh inning and Washington earned a split of the day-night doubleheader with a 5-2 victory over Atlanta on Saturday night.
The Braves won the first game 4-0 behind Ben Sheets' strong performance.
Instead of another loss and barely maintaining its division lead, John Lannan helped Washington snap a three-game losing streak and move ahead of Atlanta in the NL East by 2½ games.
"I think most of the guys in this locker room felt like it was a must win tonight," said closer Tyler Clippard, who pitched the ninth inning for his 16th save. "If they took three from us right away, it would have been a pretty big blow. To get this win tonight, John stepped up in a huge way for us, pitched great and our offense came through when we needed, too. It was a huge win."
In between games, Nationals manager Davey Johnson said the MRI on Harper showed no break though he kept his centerfielder out of the starting lineup for Game 2.
Harper entered in the eighth and singled, stole second and scored on Danny Espinosa's single to right. The first-time All-Star stayed in as the right fielder in the ninth.
"It feels all right," Harper said. "Once I get going, that's when it feels good. When I sit down, that's when it feels bad."
Bernadina, who entered as a defensive replacement after Harper fouled a bunt off his left ankle in the first inning of the first game, finished 5 of 7 on the day including a go-ahead RBI single in the night game.
Lannan (1-0) pitched seven innings for the win.
In the opener, Sheets (2-0) pitched six shutout innings, Brian McCann and Chipper Jones homered. Outdueling Nationals starter Edwin Jackson (5-6), Sheets extended his scoreless innings streak to 12 in his return after missing last season because of Tommy John surgery on his right elbow.
Harper gave signs that he would play in the second game when he stepped into the on-deck circle in the seventh.
After Sandy Leon's leadoff single and with the scored tied at two, Johnson instead turned to pinch-hitter Mark DeRosa, whose sacrifice bunt advanced Leon to second. One out later, Bernadina's grounder into right field scored Leon.
Harper's failed bunt attempt came in the bottom of the day's first inning. Limping and doubled over in pain for several moments, he completed the at-bat by striking out. Harper returned to center field in the second inning, but Bernadina replaced him on defense for the top of the third with the Nationals trailing 1-0.
The kid thought he could tough it out.
"I didn't think I broke something," Harper said. "Pain doesn't really get to me much. I think if he would have left me in there I could have played, definitely."
Riding the momentum of the earlier win -- their third straight -- the Braves jumped ahead 2-0 in the first. Jones stroked a two-out, RBI double into the right-center gap of Lannan and Freddie Freeman followed with an RBI hit.
Jones hit a two-run, pinch-hit home run in the first game.
Recalled from Triple-A Syracuse, Lannan settled down and held the Braves scoreless over the next six innings, not allowing a hit over his final four innings. Despite a 4.89 ERA in the minors, the Nationals' leader with 10 wins last season allowed only five hits, walked two, struck out three and hit two batters before the sellout crowd of 40,007.
Including Friday's loss, the Nationals failed to score for 15 innings before scratching across a run in the fifth and six innings against Delgado. Trailing 2-0, Espinosa raced home from third with two outs in the fifth on a wild pitch.
Washington loaded the bases with no outs in the sixth on two singles and a hit batter. Ian Desmond's RBI groundout tied it at 2.
Also brought up from the minors to pitch game two, Delgado allowed two runs and six hits over six innings.
In his second start of the season and with light rain falling intermittently, Sheets threw 91 pitches, allowing five hits with six strikeouts and three walks.
Jackson struck out nine to match his season high while allowing five hits and two walks over seven innings. His one mistake was McCann's solo homer in the second inning, the 16th of the season for the Braves catcher and his seventh in 10 games.
With three RBIs, Jones has 1,601 for his career. ... Nationals OF Jayson Werth (wrist) finished 1 of 3 with a walk in his first rehab assignment at Class A Potomac. ... Braves starter Jair Jurrjens faces Ross Detwiler in Sunday's series finale.