The Senators had won four straight and posted an 8-0-1 record through nine games heading into Monday's home test against Winnipeg, but the Jets recorded a 2-0 decision to deal Ottawa its first regulation setback since Dec. 27.
Ottawa enters tonight tied with Philadelphia for fourth in the Eastern Conference and is also seven points ahead of the Maple Leafs for second in the Northeast.
Monday's defeat marked the first time Ottawa has been shut out this season. Chris Mason made 25 saves to help the Jets stop a three-game losing streak. Ottawa's Craig Anderson took the loss, giving up two goals on 35 shots.
"We didn't bring our best, but I think we gave ourselves the opportunity to win," said Anderson.
Prior to Monday's game at Scotiabank Place, the Senators had played three straight on the road and tonight's tilt marks the start of a six-game swing that will take Ottawa through the end of the month. The Sens are 11-7-5 as the visitor this season.
Meanwhile, the Maple Leafs began January on a four-game winning streak, but Ron Wilson's club has lost its last two tilts, including Saturday's shutout setback against the visiting New York Rangers. That 3-0 defeat at the hands of the Rangers kicked off Toronto's longest homestand of the season. The Leafs will try to improve upon their 12-6-4 as the host when they play the second test of the five-game residency tonight.
New York goaltender Martin Biron needed to make just 20 saves to shut down Toronto's offense Saturday at the Air Canada Centre. Jonas Gustavsson, meanwhile, allowed all three goals on 30 shots for the Maple Leafs.
"I thought we came out flat a little bit," Toronto forward Clarke MacArthur said. "At this time of year there's no excuse for that. It was a big game for us and we got to have a better effort."
Toronto is currently outside the Eastern Conference playoff picture with 49 points. The Leafs are ninth in the East and one point behind Pittsburgh for the conference's eighth and final postseason berth.
The Maple Leafs hope to get centerman Tyler Bozak back tonight after he missed the last seven games with an upper-body injury. Bozak has seven goals and 18 assists this season and before getting injured he had been centering Toronto's top line with wingers Phil Kessel and Joffrey Lupul.
After dropping a 6-5 regulation decision to the Maple Leafs on Oct. 8, Ottawa has posted two straight victories in this series. The Senators have won five of eight overall in this matchup and three of the last four in Toronto.