Another night without John Tavares started to show on the Islanders, who needed their captain to spark an offense that had plenty of shots and chances but not enough results.
Still, the Islanders should have been able to hold a one-goal lead in the third period. Instead, for the second time in as many games at Barclays Center, they gave that lead away; this time, they left without any points in a 2-1 loss to the Sabres, leaving the Isles winless in three straight (0-1-2).
Calvin de Haan's second-period goal was the only mark on the score sheet for either side through two periods. But former Islander Matt Moulson tied it at 6:20 and rookie Sam Reinhart provided the winner at 13:44, both goals coming off turnovers and misreads in the defensive zone.
An attempted dump-in to allow for a line change hit a linesman's skate and the Sabres turned the other way. Zemgus Girgensons got around Travis Hamonic into the Isles' zone and his feed across the slot found Moulson, who pushed off Josh Bailey's stick check and jammed the puck behind Thomas Greiss.
The Islanders had their chances to retake the lead, the best one coming on Steve Bernier's try from the slot off a feed from Mikhail Grabovski with just under 10 minutes to go, but Buffalo rookie goalie Linus Ullmark was up to the task.
Inside of seven minutes remaining, Marek Zidlicky tried to keep a puck inside the Sabres' zone, missed and let Buffalo off on an odd-man rush. David Legwand centered a feed for Reinhart and he beat Greiss for a 2-1 Buffalo lead with 6:16 to go.
Facing another night without Tavares, who was out with an illness for the second straight game, the Islanders were looking to the same formula that helped them rally from a 2-0 hole to grab a point against the Devils in Newark on Saturday afternoon: Keep control of the play, throw pucks on net and create some traffic.
"We have to make sure we manage the puck," Jack Capuano said before the game. "I like the way the four lines are playing, the way the six 'D' are playing. We need a better start [than Saturday]."
It was a slow build, but that strategy paid off in the second. The fourth line did a bit of banging and crashing in the corner of the Sabres' zone and Jack Eichel's clearing feed tipped out to Hamonic.
Ullmark stopped Hamonic's shot but left a rebound in the slot. Casey Cizikas and Matt Martin dove at the puck and at Ullmark, who lost his footing; the puck squirted out to de Haan, who spun and snapped a wrist shot for the Islanders' goal.
The Islanders held the lead and a 21-8 shot advantage at 13:42 of the second, but the Sabres found their legs there. They applied some pressure in front of and around Greiss, who was sharp as usual.
He was especially so when Moulson came down on a breakaway after a slow Islanders' change. Moulson went to the backhand but Greiss moved with him and got an arm on the shot, one of 12 saves by Greiss through two periods.
The opening period was far better than the one the Isles had in Newark, when they were a step slow against a Devils team that has far more pluck and effort than skill. Sunday back in their own building, the Islanders were willing to chip pucks and dig away in the corners to create offense.