Moved back to the leadoff spot by manager Dave Martinez, Harper walked twice and had a sacrifice fly and a double in four plate appearances during a 4-2 win over the Baltimore Orioles. Harper doubled in the eighth inning of a tie game and came in on Juan Soto's two-run double and the Nationals took two of three from the Orioles.
"I was able to see a lot of pitches tonight," Harper told the Washington Times after the Nationals (40-33) improved to 9-1 with him in the leadoff spot.
Harper began the night hitting .133 (8-for-60) in June, with five walks and 23 strikeouts.
"My swing has felt great," Harper told mlb.com. "I've felt great the past month and a half or so, just chasing pitches. Tonight, I tried to do the best I could to get a ball over the middle (of the plate), and I was able to do that."
The 19-year-old Soto just continues to hit. Thursday night he went 1-for-3 with a walk in the cleanup spot and enters the weekend hitting .326 with six homers and 16 RBIs over 92 major-league at-bats.
"I think we're all amazed every single day," Washington starter Max Scherzer told mlb.com. "He's a great young player. He's just enjoying himself. He's the bat we kind of need in our lineup right now, that's hot. And teams are going to have to figure out how to get him out, because it's tough right now."
Friday night that task falls to Philadelphia right-hander Zach Eflin (4-2, 3.43 ERA). He has won three straight starts, allowing four runs over 18 2/3 innings while striking out 17 batters and walking just three after pitching five effective innings Saturday in Milwaukee.
Elfin will be making his first career start against Washington, which counters with right-hander Tanner Roark (3-7, 3.87).
Roark gave up four runs on eight hits over four innings of in an 8-6 loss at Toronto on Sunday.
On May 5 he lost to the Phillies in Washington when he allowed three runs in 6 1/3 innings. For his career, he is 6-7 with a 3.98 ERA in 18 games (16 starts) versus the Phillies.
The Phillies (39-33) trail the second-place Nationals by one-half game in the NL East and trail the Braves by 3 1/3 games. Philadelphia has won seven of its last 10 games and has taken three straight series -- against Colorado, at Milwaukee and against St. Louis -- as it begins a 10-game stretch against the Nationals and Yankees.
"I think coming off this series, we anticipate a highly-competitive series against a good ballclub on the road, and it seems like we're ready for that challenge," Philadelphia right-hander Jake Arrieta told mlb.com.
Off on Thursday, the Phillies defeated the St. Louis Cardinals 4-3 on Wednesday.
Odubel Herrera hit what proved to be the game-winning home run in the seventh inning to go along with a single and a double.
"It was one of those 'Wow' moments," Phillies manager Gabe Kapler told the Courier Post. "He's so hot, but he's such an incredible athlete. It's really elite barrel accuracy. I don't know how to describe it. He just knows how to find the barrel, find the sweet spot."
Herrera is hitting .419 (13-for-31) with two doubles, five home runs, eight RBIs in the past seven games. He is 13-for-31 (.419) versus Roark.