WASHINGTON — Jason Heyward singled and Justin Upton doubled in a three-run eighth inning Wednesday night in the Atlanta Braves' sweep-capping 6-3 win over the Washington Nationals, a game played nicely by both sides one night after a fastball to Bryce Harper's thigh cleared both benches. Upton also homered, and Kris Medlen (9-10) allowed three runs and three hits over seven innings as the Braves won their 13th straight to take a staggering-for-early-August 15½-game lead over the second-place Nationals in the NL East. While Atlanta has a ways to go before it can mathematically clinch, the three-game dismissal of Washington was undoubtedly a psychological clincher that only could be undone by a monumental collapse.