Aaron Nola bounced back from a string of lackluster outings, surrendering three runs (two earned) over 5 1/3 innings. He also collected eight strikeouts.
Tommy Joseph and rookie Jorge Alfaro each homered in the losing effort.
"He's making a great impression," Phillies manager Pete Mackanin said about Alfaro. "As I always say, everybody is auditioning all the time and he's having a very good audition."
Alfaro is hitting .355 with a pair of homers and seven RBI since making his season debut on August 5. He also has an .868 OPS over 65 plate appearances and appears well on his way to proving he's deserving of the the starting role come 2018.
"Do what I need to do and show what I'm capable of, that's all I can try to do right now," Alfaro said earlier in the week.
Trailing entering the sixth, Trea Turner lashed a two-run single to center to push the Nationals ahead and secure the victory for starter Tanner Roark, who lasted six innings while surrendering three runs on seven hits.
Stayin' Alive
Odubel Herrera's two-out double in the third inning extended his hitting streak to 20 games, marking a career high and the longest streak in the Majors this season. Since returning on Monday following a stint on the disabled list with a hamstring strain he's 4-for-9 and has raised his season batting average to .291.
Division Crown Awaits
The Nationals' magic number to clinch the division now sits at four, thanks in part to Miami's walk-off victory over Atlanta. The clinch will mark the second straight year the Nationals will have won the National League East division. Washington has spent the last 154 days sitting atop the division.
What's Next
The Phillies and Nationals resume their series on Friday with right-hander Jake Thompson scheduled to oppose righty Max Scherzer. Scherzer had his last start cut short as he exited after five innings with a calf issue.
____________________________________
Follow Patrick on Twitter: @PGordonPBR