The Devils dominated all the game with a 16-1 shot advantage in the first period, but Anthony Stolarz's kept the Leafs in the game.
"They have the best goaltending in the league on the other side of the ice," Keefe said.
Keefe added he thought it was the Devils "best game of the season" and added, "I leave here feeling pretty good about our team tonight."
Anthony Stolarz signed a two-year deal worth $5 million deal with Toronto after Sheldon Keefe's departure and improved his record to 9-5-2.
His league-leading .928 save percentage and 2.13 goals-against average show his importance in the Leaf's success this season.
"In the first five minutes of the game they had seven shots, so I think when a team is going to pepper you pretty early on and kind of get you in a groove, it's kind of up to you to stay in there and just keep battling," Stolarz said.
"They're an offensive team with a lot of skill, so they're throwing pucks at the net and getting traffic around there. So, it's just up to me to kind of battle through, make the saves, and not give up any second-chance rebounds."
Meanwhile, the Devils' offseason acquisition Jacob Markstrom holds a 13-6-2 record with a .906 save percentage.
Despite a solid debut of the season, Markstrom took responsibility for the loss after a shorthanded goal allowed to Pontus Holmberg and Auston Matthews' breakaway winner.
Both teams remain in the playoff hunt and Toronto now sits two points behind Florida for the Atlantic Division lead, while New Jersey are right behind Washington in the Metropolitan.