They now need their prized arm to return to form when they face the Colorado Rockies in the second game of a three-game series Tuesday night.
Harper returned Monday from a 57-game absence because of a torn ligament in his left thumb. He went 1 for 3 with an RBI single as the Nationals won 7-3 for their third straight victory overall and eighth in 10 home contests.
Ryan Zimmerman, who returned to third base after playing left field with Harper out, went 3 for 4 after going 2 for 17 in his previous five. Adam LaRoche homered for the third time in four games and Ian Desmond went 2 for 4 with three RBIs, giving him a 10-game hitting streak against Colorado with a .472 average.
"It's a strong lineup and I don't think there's too many opposing pitchers out there that want to see it," Desmond said. ''It was nice to have Bryce back."
For the Rockies (36-47), Justin Morneau had three hits and has batted .414 with 24 RBIs over his last 18 games.
Strasburg (6-6, 3.70 ERA) is healthy, but his recent numbers aren't. The right-hander has gone 0-2 with a 7.27 ERA over his last three starts, and the latest was his worst of the season.
Strasburg allowed a career high-tying seven earned runs and eight hits with three walks in 4 2-3 innings of Wednesday's 9-2 loss in Milwaukee.
"I'm not right mechanically," Strasburg told MLB's official website. "I think it's causing (hitters) to see the ball a lot better. It happens to everybody. I just have to keep working hard."
His work at Nationals Park has been substantially better with a 5-0 record and 2.21 ERA in eight starts since losing his first home outing. Strasburg is 1-2 with a 2.84 ERA in three starts against Colorado.
He'll be opposed by struggling Christian Friedrich (0-2, 8.10), who suffered the Brewers' wrath the night after Strasburg did. The left-hander lasted four innings and gave up five runs in a 7-4 defeat.
Friedrich has surrendered 14 runs - nine earned - and 16 hits in 10 innings over two starts against Milwaukee, his only two outings this year. However, he still has his manager's confidence.
"He's got good stuff; he's got a good fastball and a real good breaking ball," Walt Weiss said. "He got a lot of swings-and-misses tonight. There's no doubt he's got good stuff."
Friedrich faced Washington (44-38) once on June 26, 2012 and yielded four runs in 4 1-3 innings of a 12-5 loss. Ian Desmond went 2 for 2 and LaRoche homered while Harper went 0 for 3.
June might have ruined the Rockies' season, as they finished the month in a 2-12 slump. Colorado, loser of 15 of 23, has gone 34 games without a win in which it's scored fewer than five runs. That's its longest such stretch since going 35 games April 25-June 2, 2012.
"It's frustrating for sure," second baseman DJ LeMahieu said. "And you just have to keep going. It just takes one game to turn it around, and hopefully that comes sooner rather than later."
The rotation has posted a 7.73 ERA in the last 15 games.
With starter Jhoulys Chacin landing on the 15-day disabled list Monday and getting replaced by Franklin Morales, the Colorado rotation is completely left-handed. The Nationals are batting .282 against lefties, which ranks second in baseball behind the Rockies (.285).