San Antonio Spurs coach, national treasure and Steve Kerr mentor Gregg Popovich recently made headlines by ruing the ascendance of 3-point shooting in the NBA, saying, “I don’t think it’s basketball. I think it’s kind of like a circus sort of thing.”

Pop’s words were a bit controversial, but they seemed to find some purchase Friday night in Boston when that great 3-point shooting team, the Celtics, lost to those renowned musclemen, the Warriors.

As noted, it was the first time in 26 games that the Warriors failed to make more 3-point field goals than their opponent. That was an NBA record. (Assignment: Write a 2015-16 Warriors story of more than three paragraphs without using the phrase “NBA record.”)

Uh-huh, it was the Celtics who concentrated on shooting from the arc Friday. They did it more often (33 shots to 31) and more accurately (36.4 percent to 29 percent) than Golden State. Kelly Olynyk was particularly pesky, with 28 points off the bench and a 3-of-6 mark from 3-point range.

The Warriors’ poor showing from long distance makes sense when you consider two of their best 3-point shooters, Klay Thompson and Harrison Barnes, missed the game with ankle injuries. With Avery Johnson doing a splendid job defensively on Stephen Curry, Golden State had little chance but to take the ball inside.

It was unconventional. It was choppy. But it worked just well enough to provide a 124-119 victory in double overtime. The Warriors wound up shooting 39 free throws, a season high, and made 31 of them. That may have been the key factor in the game.

The team’s altered mindset was vividly apparent in overtime. After Andre Iguodala slapped a 3-pointer to give the Warriors a 108-105 lead with 3:02 left in the first extra period, they played basketball for another 8 minutes and 2 seconds and did not attempt another outside shot. Not even a mid-range jumper. That bears repeating. Over the final 8:02 of a nip-and-tuck game, Golden State offered nothing but layups, contested shots in the paint and free throws.

The Dubs’ inside game may have surprised casual NBA fans, which they are drawing in droves. But it wasn’t breaking news to anyone who watches them closely. Yes, this is the best outside shooting team in the NBA. But you ignore their inside game at your peril.