NBA

Knicks’ dangerous downturn starts at the 3-point line

It doesn’t take much time for so much to change.

A little less than two weeks ago, the Knicks were a .500 team and less than one game out of the Eastern Conference’s final playoff spot. That was before five losses in six games shoved them further down the crowded standings and closer to a third straight season ending short of the postseason.

In a little less than two weeks, it could become clear how closely a playoff opportunity is aligned with reality.

With five games left before the All-Star break, the Knicks face the sixth-place Celtics on Tuesday at Madison Square Garden before visiting the eighth-place Pistons on Thursday, the lone road matchup before the break.

“As we close out this first half of the season going into the break, we plan on taking care of home for the four that we have remaining,” Knicks swingman Arron Afflalo said after practice Monday. “We have 32 games left, we have some home stretches and we just got to take care of business. We’re not that far removed from being anywhere between [No.] four and 11, so with that in mind, we just got to put together a nice win streak.”

The Knicks are coming off a 21-point home loss to the Warriors on Sunday after allowing 116 points and 55.2 percent 3-point shooting, but the result was more typical than abysmal for a team facing Stephen Curry, Klay Thompson and the rest of the defending champions.

The bigger problem is the Knicks have been torched by more than just the league’s best offense lately, with their perimeter defense beginning to resemble last season’s league-worst unit.

After allowing opposing teams to hit 38 percent of 3-pointers last season, the revamped Knicks roster helped create one of the league’s best perimeter defenses early this season, holding teams to 29.8 percent 3-point shooting in November and 32.1 percent 3-point shooting in December. But over the past 10 games the Knicks have allowed opponents to hit 43.3 percent of 3-pointers.

“[There’s] some slippage in terms of not having a lot of intense practice days to really work at defending it,” Knicks coach Derek Fisher said. “Guys are facing tough situations in the game. This past month, we played a lot of really good teams that have really good guards and that impacts it as well in terms of being able to defend at a high level. Overall we put together a decent month, but we’ll have to get better in order to find some success going forward.”

Though Boston ranks among the league’s 10-worst outside-shooting teams, the Knicks defense — allowing an average of 108.6 points over the past 11 games — will not find it much easier to get stops Tuesday, facing the league’s fifth-highest scoring team.

The Knicks (23-27) have split their two meetings with the Celtics (27-22) this season — the Knicks winning at the Garden on Jan. 10 — but have allowed an average of 107 points in the two games, with Boston point guard Isaiah Thomas averaging 27.5 points.

“We just have to as a group continue to make defense our staple,” Afflalo said. “When we’re a good defensive group, we tend to be more well-balanced offensively.

“I like our personnel, I like the fact that we’re big, we’re strong, we’re physical. We just have to play a smart efficient game, and we just have to make sure we’re playing at the top of our game so we can compete.”