From the mound, the 23-year-old Strasburg reeled off 13 strikeouts over six innings, firing a career-high 119 pitches.
"Strasburg, seeing him the first time, our hitters battled him," said Red Sox manager Bobby Valentine. "He threw a lot of pitches in six innings for sure. Like they were saying, he's not just a thrower. He's a pitcher. He had pitches he could throw behind in the count. His split-changeup was a real devastating pitch. We haven't seen that out of his hand before. His fastball was alive all night long. He's special. He's a very good pitcher -- obviously."
At the plate, Harper, a 19-year-old rookie, scorched an RBI double, a two-run homer and an RBI single.
"Harper was amazing. Everything he did out there, including catching that ball that [Jarrod Saltalamacchia] hit in the gap -- the first ball hit hard there," Valentine said. "He came out of nowhere to catch that. He threw the ball from the wall -- one-hopped it to home in the ninth. He hit some pretty good breaking balls off of left-handers -- one for a hit to left, one for a groudout to short, where they almost beat it out. So he was very impressive."
It could be years before this dazzling duo performs in the same game at Fenway again, depending on what twists the Interleague schedule takes in coming years.
"It was unbelievable. I love those kinds of atmospheres," Harper said. "Philly, Turner Field with the Braves, here -- you always rise to the occasion. I love playing in these situations, and I feel like everyone does. Having a great fan base like that, coming in to play the Red Sox is always fun."
At one point, the Red Sox seemed on the verge of a dramatic comeback.
Down, 7-2, in the bottom of the sixth, Boston created a chance to climb back into the game against a possibly tiring Strasburg. Dustin Pedroia stroked a one-out single, and Adrian Gonzalez ripped a double off the Green Monster. David Ortiz walked to load the bases.
While Nationals manager Davey Johnson had relievers stirring in the bullpen, he stuck with Strasburg. The righty struck out Saltalamacchia and Kevin Youkilis, and just like that, the threat was over. Youkilis fumed after taking strike three looking, and he was ejected by home-plate umpire Doug Eddings.
"I thought we had really good at-bats [against Strasburg] right until the last one," said Valentine. "That's an RBI there. The bases were loaded, as far as I'm concerned. Youk gave him a heck of an at-bat. You know, he gets called out and the inning is over. But I think the inning should have continued. Who knows, we might have tacked on three more, four more earned runs on him."
Instead, Strasburg finished his night with a flourish.
"I don't care what his pitch count was," Johnson said. "I was going to have to fight ownership if I let him go on too long. But I didn't want to have to fight Stras' if I wanted to take him out. But it was such a great effort."
Without question, this was Red Sox lefty Felix Doubront's worst start of the season. He lasted just four innings, giving up eight hits and six runs. He walked two and struck out six.
"Felix was off, obviously," Valentine said. "He wasn't ahead of hitters. He pitched a little more tentatively than he's pitched most of the year. He's working his curveball early in counts rather than his two-seamer. He was just a little off tonight, for sure."
It was hard to remember by the end of the night, but the Red Sox actually broke out first in this one. Ortiz drew a leadoff walk against Strasburg in the second. With two outs, Ryan Sweeney drilled a single to center. That set up Mike Aviles for a two-run double high off the wall in center.
But Doubront gave that momentum right back in the third. After a one-out walk by Danny Espinosa, Harper introduced himself to Fenway fans by lining a double to center. Ryan Zimmerman followed with an RBI single that cut Boston's lead to 2-1. Ian Desmond's two-out, two-run double to right put Washington ahead for good.
The Red Sox looked as if they were about to tie it in the bottom of the third, when Gonzalez launched one to deep right-center. But right fielder Xavier Nady reached over Washington's bullpen and hauled it back in to end the inning.
"I mean, just a good catch," Gonzalez said. "We've got the short fence that allows him to be able to get over that fence pretty easily. He just made a good play on it."
Gonzalez would later get his home run -- a solo shot to center in the eighth and No. 200 of his career.
"It feels good, but doing it on a night that we lost takes away a lot of the pleasure from it," Gonzalez said.