A long and unusual day at Wrigley Field offered the Washington Nationals a chance for reflection. After sweeping Saturday’s rare doubleheader, the first scheduled one at this stadium in more than three decades, the Nationals officially reached the midpoint of their season. And through 81 games, the Nationals are 43-38 and tied for first place in the National League East, an accomplishment given all that has transpired through the season’s first three months. They have endured injuries to every unit of the team except the bullpen. The opening day lineup lasted seven innings. Five of their eight regular hitters have landed on the disabled list at some point this season, and the remaining injured player, Bryce Harper, is expected to return Monday. Their starting rotation wasn’t whole until early May when Doug Fister made his season debut, but two weeks later it lost Gio Gonzalez for a month and he has since returned. Gonzalez has hit his stride following his shoulder injury and powered the Nationals to a 3-0 win over the Chicago Cubs in the doubleheader’s first game with seven scoreless innings that snapped the team’s three-game losing streak. Blake Treinen made a spot start in the second game, and the offense came to life, boosting the rookie to his first major league win, a rain-interrupted 7-2 victory. The Nationals completed an exhausting seven-game road trip with the first scheduled doubleheader at Wrigley Field since 1983. Because of a pride parade in the same neighborhood Sunday, the two teams agreed long ago to play two games Saturday to alleviate traffic. Before a rare Sunday off-day, the Nationals had to play two games in one day, but they would return home happy and still in first place.