The day after Dennis Smith Jr.’s spectacular Sunday performance, the Knicks’ point guard of the future was slated to go on a food-shopping date. And it wasn’t just any food-shopping date.

Knicks coach David Fizdale talked with Smith on Saturday after he benched him in the fourth quarter of Friday’s first game out of the All-Star break.

The lengthy player-coach discussion centered on nutrition, Fizdale advising him to get into better shape and rely more on the club’s sports dietician.

Whatever Smith ate in those 24 hours surely worked. On Sunday night, Smith had fans less worried about Kyrie Irving’s summer decision after a 19-point, 13-assist, zero-turnover outing in the Knicks’ home-losing-streak-busting 130-118 win over the Spurs.

After Monday’s practice, Smith was headed to the grocer with the Knicks nutritionist, Erika Whitman, and he lauded Fizdale for his man-to-man chat.

“[It was] just his general concern for things I have going on, it really shows that he believes in me, believes in my ability,’’ Smith said.

“When you have a coach like that, you should go out and put max effort every time you get a chance. If I can get to the level they want me to be, I can consistently bring it night in and night out. I think I’m fully capable of that.”

Leading into the All-Star break after the Knicks’ win in Atlanta, Fizdale raised concerns about Smith’s stamina.

“The biggest message was to him — his conditioning level,’’ Fizdale said of his Saturday sit-down. “I challenged him to get in much better shape. I felt like the game before [against Minnesota], he was making a lot of mistakes out of fatigue. So, that was my big challenge to him.

“How we do things here, we really want to jump-start him on educating him about nutrition and what he’s putting in his body and how we go about getting in better shape at this time of year so we don’t crush his legs. And how’s his sleep? We had a good long talk about that, and I spent a lot of time with him trying to educate him on the importance of all this stuff. He really took it to heart.”

According to Fizdale, Smith had a long meeting with Whitman on Monday.

“They are going grocery shopping [Monday] together,” Fizdale said. “That’s a good thing. I think he wants to take this whole deal to another level. He understands where it’s coming from.”

The Fayetteville, NC, native admitted during All-Star Weekend festivities in Charlotte — where the 21-year-old competed in the slam-dunk competition — that he was a big fan of Bojangles’, a fried chicken chain that rules his home state. During the event, Smith tired in finishing second to Hamidou Diallo as he missed a slew of circus-like dunks.

“You keep missing all those dunks, that’s what happens,” Fizdale cracked. “You know I had to tease him. I’ve been lucky enough to coach former champions so I feel like can bust him a little bit.”

Since being the key piece in the Kristaps Porzingis blockbuster, Smith is averaging 16 points and 6.9 assists in nine games with the Knicks.

Still, the free-agent chatter is nonstop. The Knicks have enough cap space now to sign Kevin Durant and Irving, who looked aligned during All-Star Weekend.

“It doesn’t frustrate me,” Smith said of the noise. “I don’t really read into that stuff. I’m not on Twitter or Instagram right now. If that’s going on, I can’t control [it]. What I can control is how hard I work, how much I develop.”

Smith has not canceled his social media accounts.

“I’m just not on it,” he said. “Pretty much [since I became a Knick], just to lock in.”

Locked-in plenty against the Spurs, Smith didn’t realize he played 30 minutes without a turnover until his father told him Monday morning. Fizdale praised Smith for his attack mode as he whirred into the paint 20 times, calling it “an extremely high number.’’

“I didn’t know I had zero turnovers until after the game,” said Smith, whose sloppy passing drove his Mavericks coach, Rick Carlisle, batty.

“Even if I did turn it over, I wouldn’t have been focused on it. It would’ve been next-play mentality. That’s a big thing — focus on the next play whether it’s good or bad.”

But Papa Smith must have been excited at his 13-to-zero assist-to-turnover rate.

“Must’ve been,” a smiling Smith said in his Southern drawl.