BOSTON – Knicks interim coach Kurt Rambis acknowledged rookie Kristaps Porzingis probably has become a step slower defensively because of the rookie wall and played him just 20:14 Friday in the heartbreaking loss to Boston. But Rambis doesn’t believe the losing is shaking the 7-3 Latvian’s confidence or enthusiasm.

Porzingis’ failure to win Eastern Conference Rookie of the Month for February (Indiana’s Myles Turner captured it) underscored his downturn. The 7-3 Latvian had won the award for November, December and January. Minnesota’s Karl-Anthony Towns, who has swept all four monthly prizes, is now a heavy favorite to win Rookie of the Year.

“You look at how many games rookies played in college and in Europe and the travel in the NBA, it’s an adjustment process,’’ Rambis said at the morning shootaround Friday before the Knicks faced the Celtics. “It’s developing NBA stamina. It’s difficult on all of the young players. He’s young, slight, there’s going to be things he uses to his advantage and also things players will use against him.

“I see him as a warrior, competitor, a great basketball IQ,’’ Rambis added. “He’s the rare player who takes verbal instruction and puts it into physical actions. It’s frustration for everybody but I don’t see it changing attitude or mindset in anyway way, shape or form. He’s a competitor, a winner – that’s how he’s going to stay. It’s part of his makeup.’’

Late Friday at TD Garden, Porzingis looked downcast. He got off to a solid offensive start with eight points in the opening five minutes but Rambis limited his playing time due to matchups. He only played 2:41 of the fourth quarter in finishing with 15 points, 5 rebounds and no blocks.

“It’s never a good feeling to be on the bench and no be able to help your teammates,” Porzingis said, showing rare frustration over playing time. “Since you’re on the bench, the onlyway how I could help was cheer for my teammates and that’s what I tried to do.”

In 11 games in February, Porzingis averaged 14.8 points, 5.9 rebounds and 2.1 blocks – shotblocking prowess and boardwork taking a downturn. In recent days, Rambis has stressed how he’d like Porzingis to bang a little more on the inside. “Some of it has to be with him being too much outside,’’ Rambis said. “That’s part of why we want him to be involved more inside and take some of the responsibility of being one of our bigs and duties of that position to help all of us rebound better.

“Defensive-wise, he has to be more active like everyone else. Some of it comes down to reading and reacting. It’s part of the learning process of young ball players. If you’re a beat slow, you’re not going to be able to get the shot block or contest a shot and be in position to use his verticality.”

Teams are also becoming more physical with Porzingis now that they’ve seen him more than once. “ “Teams see now he can shoot the basketball,’’ Rambis said. “So they can get up into him. When he puts it down, they can get into his body they can stop the drive, same when posting up, they’re getting up into him.’’

Rambis didn’t use veteran SG Sasha Vujacic, a DNP. As the Knicks look toward the future, Rambis has talked about a movement to play the younger guys such as PG Jerian Grant but he got in just for 3:27. Derrick Williams, whose playing time has decreased under Rambis, was also held to just 4:43 as the Knicks bench mustered just 17 points to Boston’s 35…The Knicks host Detroit Saturday and will face Long Island’s Tobias Harris for the first time since his trade to the Pistons.