Pageau had been sniffing around the Sabres net in the latter half of Monday's game and was eventually rewarded, backhanding in the game-winning goal at 15:08 of the third period.
The winner came on a power play late in the third period, with Oliver Wahlstrom putting a low one-timer on Ullmark, who kicked the rebound into the slot, where Pageau swatted it in. It was Pageau's seventh goal of the season - his sixth in his last seven games - and also his team-leading third game-winning goal this year.
It felt just for the French-Canadian center, who turned in another well-rounded game for the Islanders. Pageau had a breakaway chance roll off his stick in the second period and had another quality look in tight to start the third. Pageau also won nine of his 12 faceoffs on Monday.
"My confidence is good," Pageau said. "I'm just trying to do the right things and come to the rink and bring some energy, bring a smile, make the boys laugh, make Marty laugh. I'm just trying to do my best, things are bouncing my way right now so I just have to keep going in the same direction."
Pageau's goal wouldn't have been possible without Wahlstrom, who did not start the game on the power play, but was rewarded for another strong effort with power-play time in the third. Wahlstrom certainly wasn't afraid to shoot, with five shot attempts - including two on net - in the game.
The Islanders held the fort from there, with Varlamov (34 saves) coming up big in the final minute.