The Nationals won their fifth straight game, but will still be the only major league team this season to finish with fewer than 60 victories. They go into the final weekend of the campaign with a 57-103 record.
Livan Hernandez (9-12) went 6 1/3 innings to collect the victory. He allowed three runs on nine hits.
Atlanta dropped its fourth in a row and slipped back into a second-place tie with Florida in the National League West -- six games behind division-winning Philadelphia.
Derek Lowe (15-10) was roughed up for six runs on eight hits in 4 2/3 innings to take the loss.