Mike Babcock described the 4-2 loss as a game the Maple Leafs should have won.
Playing for the first time at home in two weeks, Toronto controlled most of a Thursday night affair against the New York Rangers, only to lose in the final moments on a defensive-zone giveaway by 21-year-old defenceman Morgan Rielly.
It was the second giveaway that led to a Rangers goal, but the most costly in the 14th loss in 18 games for the Leafs.
Rielly lost the puck to Rangers forward J.T. Miller behind the Toronto goal and two passes later it was in the back of the net on a one-time laser by Rangers centre Derek Stepan. The goal came with just 1:31 left in regulation and only 59 seconds after Colin Greening tied the action at two with his first goal as a Leaf.
"Let's face it, we carried the play," Babcock said after the defeat. "We had all the opportunity, we should've won the hockey game. We turned the puck over twice and gave them two free goals."
A Brad Boyes giveaway sprung the second Rangers goal, which came midway through the first period from Mats Zuccarello, who set a new career-high with his 20th marker of the season. Zuccarello's attempt just beat the left pad of Jonathan Bernier on a goal that was confirmed by video review.
Toronto remains last in the NHL with 49 points following the loss and could be forced to play without leading scorer Leo Komarov in the days ahead.
Komarov was ejected from Thursday's action following a nasty elbow to the head of Rangers captain Ryan McDonagh late in the first period. The 29-year-old was dealt a match penalty for an illegal check to the head and could face supplemental discipline from the league.
'We all saw the hit. I'm going to let the league decide on it.' - Rangers coach Alain Vigneault on Leafs forward Leo Komarov's elbow to the head of NY defenceman Ryan McDonagh
McDonagh, who returned from a concussion only one night earlier after missing four games, was held out the final two periods for "precautionary reasons."
"We all saw the hit," said Rangers coach Alain Vigneault. "I'm going to let the league decide on it."
Komarov, who leads the Leafs with 18 goals and 35 points this season, has never been suspended by the NHL.
Facing a Rangers team that played one night earlier at home against Chicago, Toronto indeed dictated play, outshooting their Metropolitan division foe 37-20 while landing the game's first goal from P.A. Parenteau.
A likely trade chip for the Leafs ahead of the Feb. 29 trade deadline, Parenteau has seven points in seven games this month.
Save for the Parenteau redirection and late scramble goal from Greening, Rangers backup goaltender Antti Raanta was exceptional for New York. He made 35 saves, including a number of key stops in a first period which saw the Leafs outshooting the Rangers 11-3 at one point.
Bernier at the other end was given an opportunity to start and reclaim Toronto's crease with apparent No. 1 James Reimer struggling. The 27-year-old was relatively sharp with limited action, but still dropped his sixth straight start.
New York has been amongst the hottest teams in the league of late. The club, which trails only Washington in the Metropolitan Division, has won seven of its last 10 games (7-2-1) and nine of its last 13 (9-3-1).
Derick Brassard scored twice for the club, which leads the Eastern Conference with 21 points since Jan. 16.