The Phils have dropped 1 1/2 games behind the first-place New York Mets in the NL East.
But Philadelphia won two of three games against San Diego over the weekend, thanks to timely hits from Burrell.
He slugged his 29th homer of the season on Sunday night, a solo shot in the sixth inning that proved to be the difference in a 2-1 win over the Padres. He also homered on Friday night.
The Nationals' pitching staff, meanwhile, has allowed 17 homers during the team's 10-game skid.