Ottawa coach Guy Boucher labelled his team's injury situation as a disaster.
The Senators failed to close in on Montreal for first place in the Atlantic Division after falling 3-2 to the Winnipeg Jets on Sunday.
Ottawa, which is already without forward Bobby Ryan because of an injured finger, also lost three more key forwards — Mike Hoffman, Tommy Wingels and Mark Stone — against Winnipeg.
Hoffman left in the first period with an undisclosed injury while Stone took an elbow to the head from Jacob Trouba seven minutes into the third period and didn't return. Wingels also left in the third.
"At some point it felt like there was nobody on the bench, but a lot of character on our bench and our guys played to the end," said Boucher, who couldn't offer an update on any of the injuries. "I thought we deserved a much, much better fate.
"It doesn't look good. We have to wait until tomorrow to be clear and precise but right now we could be losing quite a few guys."
NHL Player Safety tweeted later Sunday that Trouba will have a hearing on Monday for an illegal check to the head on Stone.
Josh Morrissey scored the eventual winner early in the third period for Winnipeg.
Morrissey's goal came at 2:33 when his wrist shot from the blue line eluded Mike Condon in the Ottawa goal to make it 3-1.
Dustin Byfuglien and Mathieu Perreault also scored for the Jets (28-29-5), who won their second straight game. Mark Scheifele and Patrik Laine each had two assists while Connor Hellebuyck made 32 saves.
Zack Smith pulled the Senators to within a goal when a redirected pass hit his skate and went in at 5:05 of the third. Ottawa thought it had tied the game in the dying seconds but a no-goal call stood as there was no conclusive evidence to overturn the ruling.
"From what we saw it went in. The guys that were there at the net said it did, but it was inconclusive so there's not much you can do," Smith said.
"It would have been nice to push that one to overtime because I like the way we were going towards the end."
Stone had the other goal for the Senators (31-20-6), who also got two assists from Erik Karlsson and 17 saves from Condon.
The Jets were outshot 10-7 in the first period despite carrying most of the play. Six of Ottawa's shots came in the final four minutes of the period.
Byfuglien opened the scoring just 69 seconds into the game with a shot that beat Condon from the face-off circle to his left.
Perreault gave the Jets a 2-0 lead with a swing-around backhand from the top of the crease that beat Condon at 12:28 of the first.
"It was great to get off to a good start and get that goal right away. To get a 2-0 lead on the road is a great way to start a game," Jets captain Blake Wheeler said.
The Senators had some chances in the period but none better than a 2-on-1 that ended with Wingels missing an open net on a pass from Curtis Lazar.
Stone's power-play goal at 5:10 was the only marker of the second period and it cut the Jets' lead to 2-1. Stone took a pass from Karlsson and fired a quick shot from the slot over the left shoulder of Hellebuyck.
Notes: Ryan and Chris Neil were scratches for the Senators. Andrew Copp, Drew Stafford and Julian Melchori were scratches for the Jets…Heading into action Sunday, Senators defenceman Mark Borowiecki led the NHL with 245 hits, 31 more than Matt Martin of the Maple Leafs, who is second…Jets forward Shawn Matthias turned 29 Sunday…The Jets have gone five straight games without a power-play goal and are 0-14 during that time…The Senators next game is Tuesday in New Jersey against the Devils while the Jets play the last game before their bye week Tuesday against the Maple Leafs in Toronto.