Islanders goalie David Rittich reacts after surrendering a goal in the...

Islanders goalie David Rittich reacts after surrendering a goal in the final minute of the first period against Chicago at UBS Arena on Tuesday. Credit: Jim McIsaac

The Islanders were giving a clinic in how to blow a playoff spot, turning the puck over repeatedly up ice to a team that’s good on the rush.

It made them look like the team headed toward the NHL Draft Lottery, not Chicago.

Which only made the 4-3 loss on Tuesday night at UBS Arena that much more frustrating. Because the Islanders got off to a good start before stumbling, then dominated the third period with a 23-5 edge in shots to close the gap to one goal.

In all, the Islanders (40-27-5), who once again fell out of a playoff spot, outshot Chicago 47-24 and, according to NaturalStatTrick.com, had a 27-12 edge in high-danger chances.

But shoddy defense in the first period — no leniency allowed for playing with five defensemen after Tony DeAngelo (lower body) was hurt 12:46 into the match — and a shaky outing from David Rittich, who allowed three goals on 12 shots in 20 minutes, was just a smidgen too much to overcome.

“Some costly mistakes in the first period,” said Cal Ritchie, who knocked in the Islanders’ third goal at 16:47 of the third period and was wrongly implicated in a non-icing call that led to Chicago taking a 4-1 lead on Frank Nazar’s goal at 6:02 of the second period. “Chasing the game like that, we’ve been really good all year coming back in games. Can’t do it every night.

“It’s frustrating because it felt like we were all over them most of the game.”

Just how damaging the loss will ultimately prove will be determined over their final 10 games.

For now, the Senators, who won in Detroit, passed the Islanders for the Eastern Conference’s second wild-card spot. Each team has 85 points but the Senators have played one fewer game. The Blue Jackets won in Philadelphia to move into second place in the Metropolitan Division with two more points than the Islanders in one fewer game.

The lone bit of good news was the Penguins lost to the visiting Avalanche to slip to third in the Metropolitan Division, one point ahead of the Islanders in one fewer game.

“I liked our start, we came out flying,” said Anders Lee, who tipped Matthew Schaefer’s blue-line shot to open the scoring just 49 seconds into the game. “We had some turnovers that ended up in our net. Our mistakes have nothing to do with our intensity or will to win. We just messed up.”

Mathew Barzal’s blue-line turnover and lack of backchecking effort led to Nick Lardis finishing a two-on-none rush to tie it at 1-1 at 12:46 of the first period. DeAngelo exited to the Islanders’ room after getting beat up ice and the Islanders were already playing without top-pair defenseman Ryan Pulock, who missed his second game with a lower-body injury.

Coach Patrick Roy benched Barzal for a lack of backchecking in a 5-0 loss to the Sabres on Jan. 24 but said he didn’t consider it this time.

“It’s a team that has a lot of good rush players,” Roy said. “We give them that chance, that’s what’s going to happen. It’s fine that we were making mistakes but I felt we should have recovered from it. We should have backchecked and tried to protect the net front.”

Ilya Mikheyev scored on a similar rush at 18:06 and Tyler Bertuzzi pushed it to 3-1 with 28.7 seconds left in the first period when Rittich couldn’t contain the rebound of defenseman Alex Vlasic’s shot.

Nazar’s winner came after on-ice officials ruled Ritchie touched the puck on what appeared to be icing against Chicago.

“The referee said he made a mistake,” Roy said. “It was bad timing for us.”

“They said I touched the puck,” Ritchie said. “I wasn’t even near the play. It’s a little frustrating.”

Simon Holmstrom’s snap shot brought the Islanders within 4-2 at 8:45 of the third period but goalie Arvid Soderblom, who entered the match with a bloated 3.72 goals-against average and substandard .879 save percentage, ultimately held on for Chicago (27-31-13).

Notes & quotes: Anton Frondell, the third overall pick in June’s draft, made his NHL debut with an assist for Chicago after completing his Swedish Hockey League season with Djurgardens IF on Saturday. Victor Eklund, his linemate and the 16th overall pick, is expected to join the Islanders’ organization this week. Eklund signed his three-year, entry-level deal in July . . . Defenseman Isaiah George was recalled from the Islanders’ AHL affiliate in Bridgeport but was a healthy scratch.

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