Washington star Alex Ovechkin scored his 21st goal of the season and No. 727 for his career, moving within four of Marcel Dionne for fifth on the NHL list. Brenden Dillon and Jakub Vrana also scored in a game the Capitals never trailed.
Vitek Vanecek stopped 30 shots to earn his NHL rookie-leading 16th win. Washington stopped a two-game slide and improved to 6-0-1 against Buffalo this season.
Washington bounced back from a 4-2 loss to Boston that dropped the Capitals into second place in the East, two points behind the New York Islanders. The win over Buffalo moved Washington into a tie with the New York, after the Islanders' 4-1 loss to the Rangers.
''Not the effort or the result we wanted last wanted last night, so it was important for us to come out tonight and get the two points,'' Schultz said. ''It was a tough back to back, and we can move on now.''
Henri Jokiharju, Casey Mittelstadt and Tage Thompson scored for Buffalo. Dustin Tokarski made 29 saves and dropped to 0-4-1 on the season.
Tokarski hasn't won since the journeyman backup stopped 25 shots in Montreal's 3-1 victory over Ottawa on Dec. 12, 2015.
Buffalo also was playing on consecutive nights following a 6-3 loss to the New Jersey Devils.
The Capitals jumped to a 2-0 lead 11:39 in on goals by Dillon and Ovechkin, who scored when his intended pass for Tom Wilson in front banked in off Buffalo defenseman Rasmus Dahlin.
Schultz scored 28 seconds into the second period to make it 3-1, and then set up Vrana's goal. He drove up the middle and made a no-look pass into the right circle to set up Vrana's one-timer, putting Washington up 4-2 midway through the third.
''It was a big goal. Great play by Schultzy,'' coach Peter Laviolette said. ''You take a goal like that and build some confidence off it and have it moving in the right direction as well.''
Schultz said he was intending to shoot from the slot before hearing Vrana yelling for a pass.
''He's got a great one-timer. So any time you give it to him in that area, you've got a pretty good chance of it going in,'' Schultz said.
Buffalo interim coach Don Granato was pleased to see his team's youngsters begin to deliver at a time the last-place Sabres are looking to the future, with the team all but mathematically out of playoff contention for an NHL-record matching 10th consecutive season.
The 22-year-old Mittelstadt has four goals in his past six games, while Thompson, 23, has three of his four goals in his past five.
''That's a priority and it will remain a priority simply because their ceiling is so high and we need to become a better team,'' Granato said of the emphasis in developing the team's youngsters.
The Sabres displayed resolve and continued to show signs they aren't the same pushover of a team that was in the midst of an 18-game skid just two weeks earlier.
Buffalo cut the lead to one goal three times, ending with Thompson tipping in Rasmus Ristolainen's shot with 1:20 remaining.
Evgeny Kuznetsov had a goal disallowed with 3:13 remaining on a successful offside challenge by the Sabres. Replays showed Wilson was offside when Washington entered the zone.
FANS IN STANDS
The Sabres played their second game with paying fans in attendance, while the Capitals have approval from the District of Columbia to have 2,100 fans present as soon as their next home game, Tuesday against Philadelphia.
''You can hear it, you can feel it,'' Laviolette said of the eight games Washington has played in front of fans this season. ''I know everybody's excited to get back to normal, or at least start the process back to normal. So it'll be great to have fans in our building.''
The Sabres claimed forward Drake Caggiula, a day after he was placed on waivers by the Arizona Coyotes. He has just one goal and six assists in 27 games this year.
The 26-year-old Caggiula is completing a one-year, $700,000 contract. His debut with the Sabres is expected to be delayed after being required to enter the NHL's COVID-19 protocol upon arriving in Buffalo.
He adds experienced depth to the Sabres at a time when the team is expected to trade several players, including forward Taylor Hall, before the NHL's deadline on Monday.
Washington's T.J. Oshie played in his 400th career game, while it was No. 100 for Buffalo's Victor Olofsson. Sabres undrafted rookie center Arttu Ruotsalainen made his NHL debut.
Capitals: Play at the Boston Bruins on Sunday.
Sabres: Open three-game road trip starting at the Philadelphia Flyers on Sunday.
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