Two players in NBA history have scored at least 25 points and grabbed at least 15 rebounds in one game before their 20th birthdays.

One is LeBron James, among the greatest players of all time.

The other is Kevin Knox, who is nowhere close to being spoken about in those terms, but who accomplished that feat over a career-high 41 minutes in Sunday’s 119-107 loss to Charlotte at the Garden.

The ninth-overall pick in the 2018 draft netted a season-best 26 points for the second time in five games, but his 15 boards marked the first time in 21 appearances that he recorded double figures in that category.

“He’s getting better. We’re watching his growth right before our eyes,” Knicks coach David Fizdale said after the game. “Where he started struggling, really, early, you’re starting to see more games now where he’s putting together some solid performances.

“I’ve really been stressing to him rebounding and getting in the trench. We do a lot of block-out drills, just trying to get him used to the physicality of the league, trying to fast-track him that way. And so he’s taken it to heart, and he’s going to get the ball.”

Fizdale has been imploring the 6-foot-9 Knox to boost his rebounding average — still just 3.8 per game — and he even employed the rookie at power forward rather than small forward on Sunday.

“He knows when he puts me at the 4, I’ve got to go out and rebound,” Knox said. “I’m in kind of a big-man position so I’ve got to go down there, I have to fight in the paint. So he’s really been stressing it, and I have to be consistent with it and get eight, nine, 10 every single game. Especially at that 4 position.

“When I rebound more, the whole game revolves around that and I play really well because it helps me start the break and gets the ball moving really well. I just think when I rebound more, I play really well. And talking to Coach, I’ve just got to do it consistently. It’s hard as a rookie, but that’s the next step — having a good game and back it up the next game.”

Asked if he prefers power forward over small forward, Knox added: “It’s a little bit easier because I can rebound more, but that’s not an excuse. I should rebound wherever I’m at. Both positions really, I can impact both.”

With starting forward Mario Hezonja logging just 4:49 of playing time, Knox was on the court for more than 40 minutes Sunday for the first time this season, including the entire second half.

“I was tired, I’m not going to lie,” Knox admitted. “I was tired, I was getting up and down the court. But Fiz told me he was going to keep me out there, keep playing, keep competing, I just want to make sure I kept getting up and down the floor.”

Knox’s recent surge has come on the heels of a Post report quoting anonymous scouts and NBA personnel criticizing him and 2017 first-round pick Frank Ntilikina as “soft.” Fizdale also had questioned Knox’s “motor” earlier this season, but the coach believes the rookie “definitely has gotten better with that and has made some jumps” in that area in recent games.

“He’s going to the rim stronger on more plays. He’s taking that extra dribble that we’ve been talking about a long time, and it’s finally starting to turn the corner a little bit from that standpoint,” Fizdale said. “He’s running the floor harder, going after rebounds above the rim more.

“Again, it’s just a matter of his body adjusting to the physical nature of this game. I think everybody could see that’s what’s probably — his weakness is his weakness. That’s what happens when you’re 19 and you come into a man’s league. They’re going to try to beat you up. But there’s definitely a package of skills there that I’m really happy about and I think we can really grow.”