BOSTON — Last year’s Nets turnaround came from a players-only film session at their Dec. 6 practice. This time they didn’t wait that long.

If the Nets’ recent hot stretch continues, they may look back and say the seeds of victory were watered with the tears of defeat. Or halftime of one particular defeat, for clarification purposes.

The Nets came to Boston riding a four-game winning streak since suffering a 115-86 beating at the hands of Indiana on Nov. 18. Or more to the point, since an intervention at intermission of that rout.

“It actually happened at halftime of Indiana, because we were struggling,” Joe Harris told The Post. “It was just definitely more of an effort/energy thing. It was definitely one of those halftimes where guys were getting on each other. But at the same time, it was what was needed. There has to be a level of accountability in the locker room.

“We know we have a capability of being a great defensive team. We just weren’t playing hard enough, we weren’t competing enough, we weren’t communicating. We weren’t doing the stuff that’s really in our control. We did a much better job lately of being locked in on that end, and when you play good defense it translates to good offense.”

The Nets weren’t doing anything well enough in the second quarter of that rout, letting Indiana hit 7 of 10 from deep and getting blitzed 41-17. Every blown assignment and open 3 rightly embarrassed them.

So after last season’s epiphany came in a players-only film session at practice, this time they jumped on things even quicker.

“There’s been a few of those film sessions,” Kenny Atkinson said. “I always wonder how much impact do they have?

“There is time before you’ve got to hammer the message home a little more forcefully and make the players understand the importance of what you’re trying to get through. Sometimes just doing what you do with more force and better. … I’d like to think those film sessions helped to get us back on track.”

However they got there, the Nets are on track now. And it strains credulity to think that halftime session didn’t play a huge part.

“After Indiana it had nothing to do with the scheme, guys’ talent level,” Harris said. “Since then we’ve really just locked in and taken more of a short-term approach where we’re really just trying to hold guys to less than 25 points a quarter.”

Up to that point, the Nets defense had been as stout as wet paper, ranked 22nd. But since, they have the best Defensive Rating in the NBA at 101.0.

“It’s the defense, man. At the end of the day that’s all it comes down to,” Spencer Dinwiddie said. “And that should be a Nets theme regardless of who’s playing. This is not something that’s this group or that group, he’s in he’s not in.

“If we as a unit can hold a team to 100 points then we have a chance at winning. Obviously when we have Kyrie [Irving] and them, the chance is a lot higher, You feel me?”

The Nets are 5-1 since losing Irving to a shoulder impingement, but Dinwiddie is bright enough to hear the hot takes and preemptively push back on the narratives. He said not only can they defend this way upon his return, Dinwiddie said they have to.

“We can’t take his talent and safety net for granted,” Dinwiddie said. “If we play this style of defense and add in one of the most talented offensive players from the point guard position in history, you’ve got a really good chance to win a lot of games.”