In one game, nothing can be done to undo the damage to the Rangers’ once-lofty standing and confident psyches after a 14-game slide into the NHL’s deeper waters.

But on Tuesday night at the Garden, the scene of Sunday night’s 7-3 rout by the Capitals, the Blueshirts have an opportunity to move into the four-day Christmas break on a positive note.

One game against the Ducks will not erase the memory of the defensive gaffes that have made the Rangers resemble an AHL team more than a club that has reached the Eastern Conference finals in three of the last four years.

One game won’t end Henrik Lundqvist’s slide. He has allowed at least four goals in three consecutive starts and in four of his last five appearances.

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One game won’t miraculously reverse the inexplicable inability to prevent quick-strike goals immediately after either scoring one or allowing one. The Blueshirts have allowed two goals in a two-minute span five times in the past six games.

To be fair, the Rangers were not as good as they looked at 16-3-2 and they’re not as bad as they look at 3-9-2, a slide that began with a 5-1 loss to Montreal on Nov. 25. Lineups have been shuffled, players have vowed to be more accountable and Alain Vigneault — who will coach his 200th game for the Rangers — insists that he believes in his group.

Perhaps the Ducks (12-15-5) — who will be playing the second game of a back-to-back after Monday night’s 5-2 loss to the Islanders — will be less difficult to handle than the Eastern Conference-leading Capitals, who are nine points ahead of the Islanders and 10 points ahead of the Rangers in the Metropolitan Division. The Rangers have won four of the last five home games against Anaheim.

The Rangers didn’t practice Monday, but defenseman Kevin Klein, out since Nov. 30 with a strained oblique, could return Tuesday night. They will regroup during a full morning skate at the Garden on Tuesday.

Blue notes

It appears likely that Dan Girardi (right knee) and goaltender Antti Raanta (head injury) won’t be back until at least Monday, when the Rangers visit Nashville . . . Carl Hagelin, who played parts of four seasons with the Rangers before being traded last summer, returns to the Garden for the first time with the Ducks.