The left-hander was sidelined since mid-April because of a strained quadriceps tendon in his right knee. He said he wished he would have made it a bit deeper into the game -- he needed 92 pitches to get through five frames -- but added it was "awesome" to be back on the big league stage.
"It's been a pretty long time, it kind of flew by, but a lot of hard work to get back to this point," Lannan said. "And I'm glad to be back."
Lannan signed a one-year, $2.5 million deal with the Phillies in the offseason, but he was with Washington from 2007-2012. Though he spent a good portion of last season in Triple-A, Lannan pitched in 134 games in his six seasons with the Nationals, including Opening Day starts in both 2009 and '10.
However, he said that history did not change his approach.
"I knew I had to do a job no matter who I was facing," Lannan said. "They have some good hitters over there, so I really had to bear down at times. But there was no extra emotion."
Lannan had a tough start to the game. He put runners aboard with a walk and hit batter in the first inning, then allowed a one-out RBI single to former Phillie Jayson Werth to put the Nationals on the scoreboard.
Lannan gave up at least one hit in each of the first four innings, but buckled down at a crucial moment. Lannan had a three-up, three-down fifth inning against the heart of the Nationals' order, which took some pressure off the Phillies' bullpen.
And though Lannan would have picked up his first win as a Phillie if Jonathan Papelbon hadn't allowed a ninth-inning homer to Chad Tracy, the starter was still happy with the work the Phillies' relievers were able to do -- which included two perfect innings from Michael Stutes.
"Stutes did a great job, the bullpen did a great job tonight," Lannan said.
Lannan lowered his season ERA to 5.49, but he had just one rough start in four outings this season. Against the Reds on April 17, Lannan allowed six runs in 1 2/3 innings, but that was the game in which he injured his knee. He posted a 3.00 ERA in his other three starts.