Strasburg pitched well Tuesday night in the Nationals' 3-0 loss to Miami, the Marlins' sixth straight win.
Strasburg (7-9) allowed one run and four hits in seven innings. He gave up four runs in each of his last two starts.
"I just tried to keep the ball down and less contact and really move it in and out," Strasburg said.
The Marlins got to Strasburg in the sixth when Giancarlo Stanton drove in his first of two runs in the game.
"That might be the best that I've seen him pitch," Marlins manager Mike Redmond said. "He had a really good fastball going. He's had some struggles the last couple of years pitching here in Miami, but tonight he was sharp."
Miami was led by its two All-Stars in Stanton and Henderson Alvarez (8-5), who pitched seven innings of three-hit ball.
Christian Yelich also drove in a run for the Marlins, who have won nine of 10.
At 53-53, the Marlins have climbed back to the .500 mark for the first time since June 25 when they were 39-39. They trail the Nationals by five games in the NL East.
"They've got the ability to roll off like they're rolling right now," Nationals manager Matt Williams said.
Yelich hit an RBI double in the eighth to give Miami a 2-0 lead and Stanton drove him in two batters later.
Bryce Harper had two of the Nationals' five hits.
Nationals: There is still no timetable for Ryan Zimmerman, who was put on the 15-day disabled list on July 23 with a pulled hamstring. "The first two weeks are key," Williams said. "So once it gets healed, it starts to mat down a little bit and then you can start doing some strengthening exercises and then you get a better idea of where he would be."
Also, plate umpire D.J. Reyburn took a pitch off his right wrist in the top of the seventh inning, delaying the game for nearly 5 minutes. In the ninth, Reyburn was struck in the right knee and play was momentarily halted.
Tanner Roark (10-6, 2.82) will start for the Nationals in Wednesday's series finale against Brad Hand (2-2, 4.19). Roark has allowed one run in seven innings in each of his three previous starts with a 3-0 record. Hand is coming off his best outing of the season, pitching 7 1-3 scoreless innings at Houston on July 25.