Alex Muyl added two late insurance tallies for Nashville, who moved up to third place in the Eastern Conference standings while extending their unbeaten record at home in 2021 to 12 matches (seven wins, five draws).
Midfielder Dax McCarty registered a win while making his 400th career MLS appearance, logging a 77-minute shift in his second season with his fifth league side.
Manager Gary Smith's squad has won three in a row at Nissan Stadium and six of their last eight there, which could make finishing in the top four to guarantee at least one home match in the 2021 MLS Cup Playoffs especially important.
Frederic Brillant also scored from an early corner kick for the Black-and-Red, who saw a five-match unbeaten run snapped on a night they could've moved above Nashville and into third place with their own victory.
- THE BIG PICTURE: Sapong grew up in D.C.'s Northern Virginia suburbs and always seems to save his best for games against the Black-and-Red. He now has nine goals against D.C. in 22 career MLS appearances (16 starts) across four clubs. But Sunday marked his first brace against his hometown side.
- MOMENT OF THE MATCH: It may get lost on a night that marked the most goals conceded by D.C. United this season and tied their worst margin of defeat, but Kamara's first-time volley on a gorgeous, over-the-top ball from Paul Arriola was proof that Route 1 Football can be beautiful.
- MAN OF THE MATCH: CJ Sapong. Beyond his brace, he was an absolute workhorse over his 84-minute shift, leading Nashville in duels contested (16), duels won (9), fouls suffered (5) and key passes (3). His first goal also helped reverse momentum after it appeared Nashville might be headed toward another slow start that doomed them to settle for home draws early this season.