Nelson was traded to the Avalanche by the New York Islanders on March 6.
“Awesome to see him get two, his first two with us,” Colorado defenseman Cale Makar said. “You can tell in the new guys, their confidence keeps going up and up, and the chemistry in the lines is starting to get there. So it's exciting, and hopefully we can keep rolling.”
Makar had a goal and an assist, and Nathan MacKinnon also scored for the Avalanche (42-25-3), who have won nine of their past 11 (9-1-1) and were playing in the second game of a back to back after losing 2-1 at the Toronto Maple Leafs on Wednesday. Jonathan Drouin and Ross Colton each had two assists, and Scott Wedgewood made 15 saves.
Colorado pulled within three points of the Dallas Stars for second place in the Central Division. Dallas has two games in hand.
“I'm really happy with it; I’ve been really happy with the way we’ve played,” Avalanche coach Jared Bednar said. “We had a handful of chances in the first period, but they were good chances and we capitalized on them. I thought that was a little bit of the difference from the Toronto game to tonight.
“So have to be pretty happy with the effort, the competitiveness, and the execution here tonight.”
Dylan Cozens scored for the Senators (36-27-5), who have lost two straight after winning six in a row. Linus Ullmark allowed four goals on 13 shots before he was replaced by Anton Forsberg at 17:29 of the first period. Forsberg stopped 18 of 19 shots in relief.
Ottawa leads the Montreal Canadiens by three points for the first wild card into the Stanley Cup Playoffs from the Eastern Conference.
“I really liked the start of our game,” Senators coach Travis Green said. “The first seven to eight minutes, I thought [we] came out exactly how we wanted to and had a couple really good looks to go up one or 2-0, yet by the end of the period we’re down 4-0 and we’re swimming uphill a little bit.
“It’s easy to say, ‘Hey, keep playing,’ and it’s human to be down that you’re down 4-0. And it is hard. You’re not going come back many nights when you’re down 4-0 against the Colorado Avalanche.”
MacKinnon gave Colorado a 1-0 lead at 10:29 of the first period with a wrist shot from above the right circle that went under Ullmark. Drouin took the puck into the zone and dropped it to MacKinnon on the move.
Nelson extended it to 2-0 at 11:28 on a wrist shot from the left circle that beat Ullmark glove side. Sam Malinski brought the puck in and cut back at the blue line, opening Nelson up for an uncontested line toward the net, before chipping the pass forward.
“On my goal, great play by 'Sammy' jumping up in the rush here, sucking in that ‘D,’ and making a nice pass,” Nelson said during intermission. “[They] had some pressure, but we weathered it. ‘Wedgie’ stood big, and then we kind of took it over a little bit.”