Detwiler was given a 1-0 lead in the second inning, when Danny Espinosa scored on a single by Kurt Suzuki.
But Philadelphia would tie the score in the bottom of the inning and then take the lead off Detwiler in the third. In the second inning, left fielder Darin Ruf hit his first Major League home run, knocking a 3-2 pitch over left-center-field wall to tie the score at 1.
Ruf faced Detwiler in college while both played in the Missouri Valley Conference. Detwiler pitched for Missouri State University, while Ruf attended Creighton University.
"I'm sure he got me in college, too," Detwiler said about Ruf.
In the third inning, the Phillies scored four runs. Carlos Ruiz highlighted the scoring with a three-run homer. It didn't help that Detwiler couldn't establish his fastball until after the third inning.
"He has such a good fastball, sometimes he gets stubborn and just throws instead of pitches," manager Davey Johnson said. "Obviously, he didn't have good feel for the ball -- a bunch of walks and not consistently down in the zone. That's what is going to happen.
"Sometimes, he has a great fastball, but he also has a good changeup and curveball. He has to learn to try pitch with them instead of trying to overthrow [with his fastball]."
The Nationals would force starter Cole Hamels' pitch count to go up to 99 pitches before he left the game after five innings, scoring two runs in the fifth. Bryce Harper sent Suzuki home on a single to center field, while Harper scored on a single by Ryan Zimmerman to make it a 5-3 game in favor of the Phillies.
"Today wasn't one of his better outings," Phillies manager Charlie Manuel said Hamels. "I give their hitters a lot of credit. They were definitely making him pitch. He's pitched against them quite a bit in the past, and they were determined. I felt like that was one reason he got to 99 pitches.
"He only walked one guy, but at the same time, he got behind on some guys. But he's had a big year for us. I don't know where we'd be without him. He's been the guy that pitches the game that gets us out of trouble a lot."
If only Detwiler avoided disaster in the second and third innings. There was a chance the Nationals could have won the game.
"The worse part about it was that the team came back in [the fifth inning] and they really fought back," Detwiler said. "We had a chance to win that game, and I put us in bad situation. That loss is completely on me in that second and third inning."
Philadelphia would make it a three-run game in the sixth inning. Reliever Craig Stammen allowed a solo homer to Domonic Brown. It almost turned out to be a nightmarish inning for the Nationals. Stammen left the game with the bases loaded and two outs. Michael Gonzalez then induced Chase Utley to ground out to first baseman Adam LaRoche to end the threat.
The Nationals could do nothing against five Phillies relievers as their march toward the NL East title stalled in the series opener.
"We just have to win tomorrow," Johnson said. "Ross battled today. We have to win the battle tomorrow. We want to win the war."
The Nationals had a chance to win the East in Philadelphia, but that will not happen with Tuesday's loss. It sounded as if Detwiler wanted to win the title at Philadelphia because the Phillies have clinched the division three times in the last five seasons at the expense of the Nationals.
"We could have celebrated on their field like they have on our field. And I didn't let that happen," Detwiler said.