Jayson Tatum was giving a poised interview after the Celtics held off the Warriors at home in overtime, and Skip Bayless was impressed.

Tatum had earned an endorsement from Bayless, a notoriously tough grader of athletic performances, for both his play and his maturity.

“I don’t know Jayson Tatum — only know of him through Nelly — but every time I watch him interviewed he comes across as an all-time Good Guy,” the FS1 “Undisputed” host tweeted Thursday night. “As great off the court as on it. The NBA is blessed to have him representing it. Thank you, young man.”

Of course Bayless knows of Tatum’s play on the basketball court; he elaborated in an interview with The Post on Friday about the close relationship the two share with the rapper Nelly, and how Bayless has been hearing about the drive and personality since Tatum was in high school.

Bayless’ relationship with Nelly dates back more than 15 years to shortly after “First Take” launched as a standalone show, after a run as “First and 10” debate segments within the former ESPN2 morning show, “Cold Pizza.”

Stephen A. Smith had not yet become Bayless’ co-host. At the time, Bayless still had a rotating cast of debate foes.

Bayless recalls his wife, Ernestine, who was then a PR executive in New York, having a connection with Nelly, who was a gigantic sports fan and wanted to come on the show. Jay Crawford was the moderator.

“Some of the executives at ESPN were on pins and needles as to whether he’d be OK on live TV, because obviously you have to clean up your act a little bit if not a lot,” Bayless said. “He’s a pro’s pro so he got it and we didn’t have any out of bounds. It was great. He actually debated me. He really, really knows and gets sports. He could have played professional baseball if he pursued it. We just clicked and we had him back numerous times.”

Bayless revealed that there was actually strong consideration given in 2016 to Nelly becoming the co-host of “Undisputed,” before FS1 landed on Shannon Sharpe. Ultimately, Bayless says, Nelly concluded that he would not have been able to make the grind work without giving up touring or other travel related to his music career.

“I would consider having him as a regular co-host on a digital show or something because he’s very good at it,” Bayless said. “He’s very strong on camera. He’s forthright, convicted and passionate in his opinions, and he’s a part-owner of Michael Jordan’s basketball team [the Hornets] — so he’s inside the NBA.”

The rapper and TV host have remained close, texting often and occasionally talking on the phone. Years back, Nelly actually gifted Bayless one of his prized possessions. Bayless grew up in Oklahoma City as a big St. Louis Cardinals fan and revered Hall of Fame pitcher Bob Gibson. Before Gibson died in 2020, Nelly obtained a signed baseball from him to give to Bayless.

“I display it proudly in my house — I’m not a memorabilia collector, but that means as much to me as anything I have in my possession,” Bayless said.

Nelly went to high school in St. Louis with Tatum’s mother and has known the hooper, who grew up in the same neighborhood, since he was a toddler.

“He began to tout me on Jayson when he was in high school,” Bayless recalls. “He said, ‘High character. Tough. Incredibly Talented. And just a great kid on and off the court.'”

Bayless thus kept a close eye on Tatum as he played at Duke and later blossomed into an All-Star on the Celtics. Tatum’s interviews also blew him away.

“Every time I watch him interviewed, he’s just stunningly salt of the earth. He’s so commanding and open-hearted and forthright,” Bayless said.

But he maintained a critical eye, and has heard about it from Nelly.

“In the Finals he’d get upset with me because I was calling him Jayson Turnover because he was out of control turning the ball over,” Bayless said. “Tatum had so many more than anyone in the playoffs that it was laughably sad. Obviously, between him and his co-star Jaylen Brown, the turnovers were the undoing of the Celtics in the Finals.”

Tatum had several turnovers in the final minutes of Thursday’s game, but overcame them in large part due to Tatum’s 34-point, 19-rebound performance.

“His character, his backbone, his St. Louis toughness, is to me what propels that team,” Bayless said. “Last night, they said, basically, not in our house. We are better than you. Remember Steph hit that shot, that 60-footer from half court, and ran off the court yelling, ‘This is my town.’ Well, it was for awhile, until Steph went 1-for-7 in the fourth quarter and 0-for-5 from 3, so it wasn’t his town that time.

After Bayless tweeted about Tatum’s poise Thursday night, he received a text from Nelly.

It read: “He’s really come into his own this year. I know he was pretty upset about how last year ended. Soooo, he definitely is using last year’s season as fuel.”

Said Bayless: “He’s been saying that all year. I believe so much in Nelly, that if he believes in Jayson, I’m all ears. I’m believing in Jayson.”