NBA

Kristaps Porzingis has hit the rookie wall — for real this time

There was a false alarm in mid-December, starting with a three-game West Coast trip in Utah, Sacramento and Portland. It looked like Kristaps Porzingis had hit a rookie wall.

His shooting slump lasted close to 10 games, but he did other things and he shook out of it in a big way. He went on to win Rookie of the Month for December and January — still blocking shots, rebounding, making athletic plays that made you go, “Wow.’’

This period of early February — with the All-Star break looming next week — is even difficult for NBA veterans. But it sure does look like the man known on T-shirts as “KP6’’ is hitting the rookie wall for real this time.

Meanwhile, the Knicks’ other key rookie, first-round-pick point guard Jerian Grant, is not improving while exiled Tim Hardaway Jr. is becoming an important piece in Atlanta, suddenly.

Grant played six seconds in Detroit — with TNT’s Charles Barkley even wondering what the deal is with the Notre Dame sparkplug, who often looks confused. Coaches keep telling Grant he is thinking too much and he should just play on his instincts.

Meanwhile, there is nothing to tell Porzingis, who simply looks gassed, and that’s no surprise. The Latvian rookie has been a lethargic shell the past three games — low-lighted by his five-point, four-rebound (none on the offensive glass) no-show in Motown Thursday.

Porzingis shot 2 for 9 and missed a couple of easy ones early that seemed to shake his confidence for the first time. His shooting percentage is down to 42 percent. When the Knicks made their giant comeback from 27 points down to take a two-point lead, Porzingis mostly stood out of the way. He played just 9:35 of the second half.

It was Porzingis’ 51st game after playing 50 all of last season in Spain, averaging less than 20 minutes.

Against Golden State and Boston, Porzingis’ defense was the bigger issue. Draymond Green blew by him on a few occasions. Against Boston, the Celtics bigs Kelly Olynyk and Tyler Zeller seemed to outmuscle him. Porzingis has snared just 15 rebounds — that’s Amar’e Stoudemire numbers.

Porzingis talked about the All-Star break being a good reprieve to which he is looking forward even with him playing in the Rookie-Sophomore game Friday night in Toronto.

“Everybody can use some off time but I might be in the gym — I might rest a couple of days and want to be in the gym,’’ Porzingis, a gym rat, told The Post. “But it’s good for everybody to disconnect for a moment and bring everyone back to see that goal we have.’’

• Coach Derek Fisher hoped the second-half comeback would be a momentum-builder as they showed a no-quit element. But make no mistake, Fisher was peeved he needed to give an important halftime speech about showing pride.

“We’ll find out,’’ Fisher said. “That’s what this is about. You don’t play basketball to know what the ending is. We’ll find out if this is an opportunity to become better and get closer together.’’

• Kyle O’Quinn can’t get a break from Fisher. After a DNP vs. Boston, O’Quinn got a two-minute stint in the first half before getting yanked, possibly for taking a quick outside shot the first time he touched the rock. Of course, Robin Lopez has been so solid for more than a month, O’Quinn and center Kevin Seraphin, a DNP in Detroit, have been rendered irrelevant for now.

• Stan Van Gundy seemed to call out Derek Fisher for calling the veteran Knicks “developing.’’ Yes, it seems SVG always takes a needle to the Knicks, perhaps because of brother Jeff never being appreciated by owner James Dolan. Stan Van Gundy is an upstate Rochester guy and a proud graduate of SUNY-Brockport State who does seem to enjoy sticking it to New York City whenever he can.