It took until the fifth game on the eighth day of the season, but the Washington Capitals finally managed to put together a complete game under the guidance of first-year Coach Adam Oates and come away with a victory.

Fueled by contributions from every corner of the lineup, starting with Alex Ovechkin and on to Joel Ward and John Erskine, Washington played a smart and aggressive brand of hockey to capture a 3-2 victory over the Buffalo Sabres on Sunday afternoon at Verizon Center. It was the only reward the Capitals wanted after days of making gradual progress with their new coach and new system.

“I think to get that first win this year, it kind of got the monkey off our back,” said Erskine, who scored his first goal since May 4, 2011, in the second period. “I think guys will be a little bit at ease. It’s not so much pressure now. And I think we got a good thing going here and we just got to keep rolling.”

Washington’s first victory had its roots in a 3-2 overtime loss two days earlier in New Jersey. While they were defeated by the defending Eastern Conference champions, the Capitals discovered their mental fortitude in rallying from a two-goal deficit and proved to themselves how well they could play if they stuck to the game plan.

“Hopefully the New Jersey game gave us confidence that when you do it right we look like a real team,” said Oates, who earned his first win as an NHL head coach.

The Post Sports Live crew wonder whether there is a direct correlation between Alex Ovechkin’s individual goal-scoring and the Capitals’ wins and losses. (Post Sports Live)

Every player agreed it was important to build off of that performance. That’s exactly what the Capitals did against the Sabres.

“The main thing is that we carry on what we started in Jersey and just played the right way today, just by chipping pucks and outworking those guys,” center Mike Ribeiro said. “I think Jersey, the one point was what we deserved, and today I think fully two points. The way we played, we played smart, we chipped pucks, we didn’t play too much in our zone. We just played smart hockey today, and it paid dividends.”

Buffalo, which was without top scorer Thomas Vanek (nine points in four games), took a 1-0 lead on a goal by Tyler Ennis 9 minutes 34 seconds into the first period. But rather than be rattled, the Capitals pushed harder and stuck to the basics.

With four minutes left in the first, a simple play by Ward to move the puck back down low and keep the play alive in the offensive zone led to his tying goal. Ribeiro gathered the puck and drew the Sabres’ attention before passing to the corner, where Jason Chimera shot into the left pad of all-star goaltender Ryan Miller (27 saves). The puck bounced out in front where Ward fired to make it 1-1.

At the start of the second, Erskine stepped up offensively in just his second game of the season. From his spot high in the offensive zone along the left boards, the defenseman faked a shot, stepped around Sabres forward Drew Stafford and fired a wrister that deflected off Cody Hodgson’s stick in front to make it 2-1.

Erskine’s tally gave the Capitals just their second lead of any sort this season and alleviated the pressure that had been building after four games of chasing their opponents. Washington didn’t relinquish the advantage for the final 36:42 of the contest, despite Buffalo adding a second goal from Marcus Foligno after Ovechkin found his scoring touch once again.

After four games without a goal, the longest drought of his career to start a season, Ovechkin cashed in from the left side with a power-play goal reminiscent of his Hart Trophy-winning years to give Washington a 3-1 edge 5:11 into the third. The play, a perfect setup by Mike Green at the top of the circle and a blistering one-timer by Ovechkin, was a familiar and welcome sight.

“I knew it was gonna come sooner or later,” Ovechkin said, quickly turning the focus to the larger milestone of the team’s first win. “I think today we play very well offensively and start play responsible and defensive. And I think it’s conditioning stuff. We’re get in shape and you can see how we move. We stop. We not make circles. And it’s working. You can see how we play today.”