The Islanders' Robin Lehner looks on during a timeout in...

The Islanders' Robin Lehner looks on during a timeout in the third period against the Rangers at Madison Square Garden on Wednesday. Credit: Jim McIsaac

It might be time to worry, particularly about the way the Islanders’ recent inability to play a full 60 minutes.

The Islanders were routed for a second straight game and leaky defensively for the third 

time in a row in a 5-0 loss to the Rangers on Wednesday night at Madison Square Garden, snapping their eight-game winning streak in the New York rivalry.

This time, it was an awful first 8:04 that doomed the Islanders (10-8-2) as they fell behind 3-0, allowing rookie Filip Chytil to score just 29 seconds into the game.

“We’re not on the same page to start,” defenseman Ryan Pulock said. “We need to be ready to go from the puck drop and be at our best right when the game starts.”

The Islanders allowed four, second-period goals in Sunday’s 6-2 loss to the Stars at Barclays Center. And the Islanders spotted the Rangers two goals in the first 5:35 last Thursday in Brooklyn before rallying for a 7-5 win.

So that’s 16 goals allowed in their last three games.

“The last two games have been awful,” said captain Anders Lee as the Islanders continue a stretch of four games in six days on Friday afternoon against the Devils at Prudential Center. “That first 20 minutes, it’s got to be good.”

“I thought the first two goals, they didn’t have any pressure on us,” Islanders coach Barry Trotz added. “They had one forechecker. The execution and the details weren’t good.”

The Islanders are still 12-2-0 against the Rangers since Dec. 2, 2015 but Wednesday

marked the Islanders’ first loss to a Metropolitan Division opponent this season after they became just the 11th NHL team to start a season with seven straight wins in its division.

The Islanders were shut out for the first time this season as Alexandar Georgiev made 29 saves. It helped him that the Islanders missed the net 17 times and had 24 attempts blocked.

Robin Lehner (22 saves) started for the first time since Nov. 10, though he made 11 saves in relief of Thomas Greiss on Sunday.

There’s obviously no excuses in hockey but it can’t be discounted that the Islanders do have a depleted roster.

“There’s some guys that are stabilizing forces,” Trotz said. “At the same time, there are guys who want the opportunity. Then this is your opportunity. Grab hold of it.”

Two-thirds of what was once considered the best fourth line in the NHL is on injured reserve with center Casey Cizikas (lower body) out two to three weeks and left wing Matt Martin (upper body) missing his eighth straight game. Also, left wing Andrew Ladd (lower body), who’s been in and out of the top six this season, is out indefinitely.

The reconstituted fourth line of burly Ross Johnston and rookie Michael Dal Colle, playing in his sixth NHL game, alongside fellow Bridgeport (AHL) call-up Stephen Gionta was the only one Trotz did not juggle in the third period.

Plus, with right wing Cal Clutterbuck (illness) out, the Islanders’ penalty kill was further impacted.

The Rangers took a 3-0 lead at 8:04 of the first period on Neal Pionk’s power-play goal with Leo Komarov – one of the Islanders’ other top penalty killers – in the penalty box for a light slash on Chytil.

Cody McLeod’s deflection of defenseman Tony DeAngelo’s shot from the right point to give the Rangers a 2-0 lead at 3:30 came after defenseman Scott Mayfield’s turnover as he retrieved a dump-in. Mayfield’s turnover also led to Kevin Hayes’ free pass to the crease for a 4-0 lead at 17:17 of the second period.

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