Both starters, A.J. Burnett and Edwin Jackson, were dominant for most of the night, but neither factored into the decision as the Pirates won in dramatic fashion, 5-4, on a Rod Barajas walk-off homer.
Strong pitching should continue Wednesday, as a pair of lefties -- Pittsburgh's Erik Bedard and Ross Detwiler of Washington -- will square off for the second game of the series.
Bedard has been solid in his first year with Pittsburgh, going 2-4 with a 2.65 ERA. The veteran, who is averaging 8.80 strikeouts per nine innings over his career, is leading the Pirates with 37 punchouts but is no longer considered a strikeout pitcher after undergoing three arm surgeries.
Manager Clint Hurdle, however, believes he still has the stuff to generate plenty of swings and misses.
"His breaking ball has been a power breaking ball," Hurdle said of Bedard. "You see it spinning, and it finishes so hard, it's been dynamic. It's been like a power bowling ball."
Detwiler has been a pleasant surprise to a dominant Nationals rotation, which entered Tuesday's contest with a Major League-best 2.17 ERA. The southpaw has contributed by going 3-1 with a 0.99 WHIP and team-leading 1.59 ERA.
The numbers are impressive by any standards, but even more so considering Detwiler wasn't named to Washington's starting rotation until the end of Spring Training.
After pitching into the seventh inning in his last start -- a win over the Diamondbacks -- it marked the third consecutive time that Detwiler has thrown at least six innings. With a victory Wednesday, he would match his career-best mark of four wins, set last season.
"Detwiler pitched one [heck] of a ballgame," Nationals manager Davey Johnson said following Detwiler's last outing. "The Diamondbacks are a good-hitting ballclub. He made quality pitches. I was really impressed. He gave me a good 6 1/3. He was my star of the game."
Pittsburgh's win over the Nationals on Tuesday marked just the second time in 10 series that the Pirates have won the first game.
Nationals: LaRoche, Zimmerman back
Adam LaRoche returned to the Nationals' lineup Tuesday for the first time since May 2 after recovering from an oblique injury and provided his team with the type of middle-of-the-order bat it expects of him.
The cleanup hitter went 2-for-3 with a two-run homer, his fifth of the year, to increase his average to .323 and OPS to .954.
Meanwhile, Zimmerman, who played in his first game since landing on the disabled list with shoulder inflammation, was back in the three-hole, and went 1-for-4 and scored on LaRoche's ninth-inning home run.
Rookie Bryce Harper has made his presence felt immediately, as he's reached base in all but one of nine games he's played this season. In the opener of the series, the 19-year-old hit his sixth double of the year to go along with a .905 OPS.
Tuesday's game marked the first time this season that Harper, who has also batted third and seventh, has hit out of the No. 2 spot in the lineup.
"I'll try to be patient for Zimmerman and [Adam] LaRoche," Harper said. "I think having them back in the lineup is going to make us pretty strong, and make us better. I'm going to try to get on base for them and do some things for them. It's going to be very important."
Pirates: McCutchen returns, goes deep
Andrew McCutchen hit his first home run of the year in Tuesday's win over Washington. The fourth-inning blast snapped a 134 at-bat homerless streak, and was McCutchen's first since Sept. 13, 2011.
The All-Star outfielder has been battling a stomach flu and sat out Pittsburgh's last game Sunday, and then had Monday to recover because of an off-day in the schedule. It seems to have made the difference.
"I felt good today, woke up feeling really good," McCutchen said. "So I feel like my normal self, ready to go out and start playing again. I lost a little weight, but I'm slowly putting it back on. I got my appetite back, so I'll be able to put it back quick."
McCutchen is batting .302 with five stolen bases and a team-leading 14 runs scored.