Matt Niskanen scored an equalizer in the third period, but Torrey Mitchell gave the Sabres the 2-1 lead for good minutes later with his third goal of the season.
The Caps' Michael Latta squared off against Marcus Foligno in the first period.
Barry Trotz says the Caps are beginning to show more discipline on the ice and on the bench.
The Buffalo Sabres own the worst record in the NHL, but they've outscored their opponents 10-3 in back-to-back wins. Coverage begins at 7 p.m. on CSN.