Stammen, recalled by Washington earlier in the day, pitched 7 1/3 strong innings to lead the Nationals past the Atlanta Braves 7-2 on Tuesday night.
"I had some things I had to prove," Stammen said, adding his time at Triple-A Syracuse helped him return to his strengths as a groundball pitcher.
"I had to get back to who I was and how I got into the big leagues," said Stammen, 26, a 12th-round pick from the University of Dayton in 2005.
Stammen (2-2) was sent to the minors with a 5.43 ERA on June 6 to clear room for rookie Strasburg, the No. 1 overall pick of 2009 who lost to the Braves 5-0 on Monday night.
"It's part of the game," Stammen said of the minor league stint. "You're spitting fire. I wanted to do everything I could to make it short."
Stammen allowed five hits, struck out four and walked two. He ended streaks of nine straight starts without a win this year and 10 straight road starts without a win. The right-hander's last road win came on July 11, 2009, at Houston.
Nationals manager Jim Riggleman said Stammen "showed his competitive edge."
"We needed a starter," Riggleman said. "He pitched a couple of good games [at Syracuse]. He earned the right to come back up."
Atlanta's Brian McCann said Stammen "changed speeds and kept us off-balance, really, from the start."
"He very rarely missed up. He was ahead in the count and used all his pitches. He pitched a great game and you move on," McCann said.
Atlanta's first seven outs were in the infield, including six grounders.
"When I'm getting a lot of groundballs, I'm a much better pitcher," Stammen said. "That's a good indicator of how I'm pitching."
"All in all not a very good game," Lowe said. "There's no trying to analyze it and figure it out. It wasn't the sharpest game."
Stammen left the game after giving up back-to-back doubles to Martin Prado and Melky Cabrera with one out in the eighth. Sean Burnett struck out Chipper Jones and ended the inning on McCann's groundout.
Lowe shut down the Nationals until the fifth, when Zimmerman's two-run double was the big hit in a three-run inning. Nyjer Morgan had a single to drive in a run.
Gonzalez had a run-scoring single in the sixth, and Willingham greeted reliever Peter Moylan with a two-run homer in the seventh.
Prado drove in Gregor Blanco with a triple in the third for Atlanta's first run.
Strasburg's first start in Atlanta drew a crowd of 42,889, the Braves' second-biggest total of the season. One night later, attendance at Turner Field fell to 19,045, the second-smallest of the season.
Rght-hander Cristhian Martinez, who pitched a perfect ninth, will be optioned to Triple-A Gwinnett on Wednesday to clear a spot for right-hander Jair Jurrjens to come off the disabled list and start against the Nationals. ... Braves outfielder Matt Diaz was activated from the 15-day disabled list. He replaced rookie outfielder Jason Heyward, who was placed on the 15-day DL on Monday with a sore right thumb. Diaz returned from thumb surgery and struck out as a pinch-hitter in the eighth. ... The Nationals placed right-hander Tyler Walker on the 15-day DL, retroactive to June 20, with a shoulder sprain to clear a spot for Stammen.