New York Islanders goalie Thomas Greiss (1) and defenseman Marek...

New York Islanders goalie Thomas Greiss (1) and defenseman Marek Zidlicky (28) react as Buffalo Sabres center Sam Reinhart (23) celebrates his game-winning goal during the third period of a game on Sunday, Nov. 1, 2015 at Barclays Center. Credit: AP / Kathy Kmonicek

Another night without John Tavares, who was home with an illness for the second straight game.

You would expect the Islanders to struggle offensively without their star. You would not expect two third-period breakdowns to blow a one-goal lead and leave the Isles with nothing in a 2-1 loss to the Sabres Sunday night at Barclays Center.

"There were parts of that game we completely dominated," said Calvin de Haan, whose spin-around wrist shot past Linus Ullmark put the Isles on top at 13:42 of the second period. "Sometimes it feels like we let them hang around a little bit . . . It's tough to let that one slip. You've got to beat the teams below you in the standings."

The Isles are winless in three straight (0-1-2) and have coughed up third-period leads in two of those. Despite outshooting the Sabres 30-22 and, as de Haan noted, controlling play during long stretches of the first two periods, they were up by only a goal in the third. And that left them vulnerable to any mistakes.

Then a dump-in intended to enable the Islanders to change hit a linesman's skate and sent the Sabres back with speed. Zemgus Girgensons sent a centering feed toward Matt Moulson driving the net. The former Islander fought off a weak stick check from Josh Bailey and jammed the puck behind Thomas Greiss to tie the score at 6:20.

The next misplay by the Islanders sent them to defeat. Marek Zidlicky pinched along the right-side wall at the Sabres' blue line -- "We don't do that," Jack Capuano noted -- and the Sabres broke out for a two-on-one. David Legwand threaded a pass to Sam Reinhart, who buried it with 6:16 to play.

"We lose a battle in front on Moulson, then it's a little focus lapse,'' Capuano said. "Some guys were too casual."

Tavares' illness meant the Islanders needed to be as straightforward as possible on offense. That meant possessing the puck, firing shots at Ullmark, a rookie, and battling for rebounds. That's how de Haan scored, but there wasn't much else in the way of second-chance opportunities all night.

"This was our game," Casey Cizikas said, "and we it slip away. You can't take a shift off, can't take a period off.''

"We have to make sure we manage the puck," Capuano had 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]." And he got it. But it wasn't enough.

The Islanders are 6-3-3 for a respectable 15 points through 12 games. But there have been few nights with complete attention to detail, few nights when every Islander has put forth the full effort.

Capuano had his Kid Line together for a second game in a row, but the Anders Lee-Brock Nelson-Ryan Strome trio wasn't good enough. Zidlicky made some curious decisions.

Still, it should have been enough to overcome Tavares' absence. Instead, the Isles are left hoping their captain will be well enough to play Tuesday night against the Devils.

"We're not going to make excuses," Travis Hamonic said. "You're obviously going to miss him. But you have to adapt."

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