The Islanders’ messy five-on-five game carried over from Sunday to Tuesday.

Their ability to overcome it did not.

This was a bit of a reality check for a club starting to wonder if it had turned the corner after securing back-to-back wins, getting within a third straight victory of a playoff spot and finding some needed confidence on its special teams.

The final was 3-1 to the Kings on Tuesday night at UBS Arena, and it splashed onto the Islanders like a bucket of cold water.

The Islanders looked disconnected at five-on-five for the first half of the game, struggling to complete passes and break the puck out, struggling in their retrievals and struggling to put the brakes on a Kings team which has now won six in a row.

It looked like a good team playing a mediocre team, which is how it usually looks when a legit contender comes to Long Island.

And though the Islanders put together a strong push for the back half of the evening, they couldn’t find a way to make up for starting the game nearly 30 minutes late.

This time, the five-on-four units looked a lot more like they have all season, which is to say they struggled to sustain pressure on two first-period chances, then could not come up with a tying goal when given a third opportunity in the last period.

That left Ilya Sorokin, who did indeed bail out a series of errors, out to dry without nearly enough offensive support and rarely getting a minute to breathe.

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The Islanders’ ability to clear out their own netfront was a disaster for much of the night and bit them 3:09 into the second when Sorokin tried to look around a screen and Kevin Fiala simply shot the puck the other direction, beating the goalie easily for a 2-0 lead.

Anders Lee cut it in half six minutes later by finishing Kyle Palmieri’s feed to the slot, so the game stood at 2-1 entering the third — the Islanders having a chance to complete the comeback despite having been dominated through 40 minutes.

Their late push did showcase a far better effort than earlier in the game, and a third-period power play produced chances, but nothing that found the back of the net.

Noah Dobson’s floater from the top of the zone appeared to have Darcy Kuemper fooled with 6:31 remaining, but clanked off the post.

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Less than two minutes later, Bo Horvat hit one off the post as well.

And despite a flurry of late chances, the Islanders could not do what so many teams have done to them and tie the game up late before an empty-net goal from Mikey Anderson sealed the result.

The start had proven fatal.

Adrian Kempe took advantage of the Kings’ sustained pressure in the first period, getting to the crease unimpeded while Max Tsyplakov was caught puck-watching to finish Anze Kopitar’s feed from behind the net 13:51 into the match.

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That it was the only goal scored by the visitors in the first period was a flattering reflection on the Islanders.

There was also a rough night on the part of Isaiah George, who struggled against a heavy Kings lineup, turned the puck over twice on his first few shifts and was stapled to the bench from 12:22 of the second onwards.

That’s part of the equation for the undersized rookie defender, but the timing — with Adam Pelech having started to skate with the team in a non-contact jersey and getting closer to a return from a jaw injury — is less than ideal for his chances of sticking around once No. 3 is back.

There’s no shame in having a bad night and there’s no shame in losing to a good team, but it’s now three of the last four games where the Islanders have done their best to beat themselves at five-on-five.

And whatever the results, that ought to be a concern.