Rajon Rondo, tempestuous basketball savant, brings to Atlanta an NBA personnel file that is unmatched in the annals of Hawks free-agent signings.

It is 14 years thick with testimonials to both the radiance and the risk of his particular form of sporting genius. Here is someone who has explored the opposite poles of the NBA’s classic rivalry – Boston and L.A. – and won a championship at each. Here is the same someone known to both elevate his coaches and flummox those on both ends of the court.

As Rondo once told a chronicler at ESPN The Magazine, being the wiliest man in the gym can be part blessing, part curse.

Rondo’s all of 6-foot-1, 185 pounds. And it requires a good deal of inner confidence and strength to, at 34, lug that weighty dossier cross country from where he won his Los Angeles ring only two months ago to Atlanta, where NBA titles are but rumor.

As one of a flurry of free-agent signings for a team entering a more results-oriented stage of its development, Rondo will be asked to reimagine himself a bit. Signed for two years at $15 million, he’s here to give Trae Young a little break from ballhandling. But he’s also needed to tutor Young and his callow teammates in the subtleties of outthinking the opposition, of adding the mental component to the physical.

For the first time in his NBA life, Rondo is the oldest player on his team. Now he must slide into the role of wise elder while also keeping up with the young’uns for his allotted minutes on the floor. And no one can dare say he’s not smart enough to figure out what the Hawks need of him.

Just how smart is Rondo?

“Freakishly smart,” the late Kobe Bryant once said of him.

His new Hawks teammates are warned that card games with Rondo are certain to leave them poorer. His memory is keen, and his brain is wired for numbers. He says he’s among the top-ranked Spades players in the country, for whoever might keep that list.

For a Celtics documentary, Brian Scalabrine, a former teammate of Rondo’s in Boston, recalled one episode in 2013 when Scalabrine was working the Golden State bench. Rondo is well-known for knowing an opponents’ assortment of plays almost as thoroughly as they do. Mark Jackson, the Warriors coach at the time, thought he’d try to confuse Rondo and the Celts by calling out a fictitious play: 42 cross.

Recalled Scalabrine: “Rondo looked at Mark and then looked in the air and said, ’42 cross, 42 cross’ and looked back at Mark and said, ‘You don’t have a 42 cross.’

“I was like, how the hell did he know that? ... They’re not a rival. It wasn’t a playoff series. It was an insignificant game during the middle of the week. He was the smartest player I’ve ever played with, and it’s not even close.”

Even in high school in Louisville, his coach would have him occasionally run practices. His college coach, Tubby Smith at Kentucky, said it was a challenge to keep Rondo engaged, just as it would be for any teacher with a student running ahead of the rest of the class.

It has long been Rondo’s trait to almost obsessively study opponents, burn their plays and tendencies into his brain and use that knowledge to worm his way into their heads.

“There’s a short list of guys in the league that you know are always looking over at me during the course of the game, and he’s on that,” Hawks coach Lloyd Pierce said. “Chris Paul. Rajon. DeAndre Jordan. P.J. Tucker. LeBron (James). They look over to see what you’re calling because they know your playbook.

“He’s always been one of those guys your conscious of. He’s trying to steal your plays so he can get a leg up on it defensively, how he can blow it up or take it away,” Pierce added. “His ability to do that is great. His ability to transfer that to the rest of our guys so that they can do that is even more beneficial.”

Rondo is smart in the kind of way that sometimes does not suffer those with whom he doesn’t agree or doesn’t respect. This makes him no stranger to confrontation.

He and Boston coach Doc Rivers had a famously prickly relationship. In 2015, his one season in Dallas, Rondo was suspended by the team after a heated argument with coach Rick Carlisle. He likewise was suspended in Chicago the following year for berating an assistant coach. He’s thrown punches with Paul (2018), bumped a ref during a playoff game in Atlanta (2012), been suspended for a game for directing a homophobic slur at a ref (2015), ejected and fined $35,000 for kneeing Dennis Schroder and verbally abusing an official (2019).

He is smart in a way that courts contradiction. For one day Rondo sees himself a coach or executive, on the other side of such conflicts.

Toward that goal, he has done some internship coaching at a prospects camp, working with the likes of one-and-done Bulldog Anthony Edwards. Last season, while recovering from a broken thumb in Los Angeles, he would arise at 4:30 a.m. to take part in Zoom game-planning sessions with Lakers coach Frank Vogel and his staff back in the Orlando bubble. He has shadowed GMs and schooled himself on the collective bargaining agreement just in case the front-office calls.

Now, with the Hawks, his communication skills and patience will be tested by a team that hasn’t exactly yet decoded the secret to winning. That’s going to naturally take time.

Asked about his patience level, Rondo this week said, “Obviously I continue to improve. I’ve learned from so many different coaches that you have to have patience. You can’t teach and coach everyone the same way. The last 15 years I’ve tried to be a sponge as to how coaches communicate with different players, and patience is a big key. Understand that not everyone is going to learn on your level. Some people may get it, a lot of people may not.

“That’s something I heard with Magic Johnson and why he struggled with coaching, people wouldn’t pick up on it as quickly as he understood the game. For me I’ve had a lot of younger guys I’ve played with in my career, and I think having kids (he’s the father of two) as well helps with patience. I think I’m up for the task.”

It needs to be added in here that the Hawks are getting more in Rondo than a busy and beautiful basketball mind. The body remains willing, as well, as he has added such wrinkles as boxing and yoga to his physical conditioning. Which is nice because the NBA doesn’t necessarily suit only great card players.

In his most recent game, the Lakers’ playoff clincher against Miami, Rondo had all the physical skills needed to produce 19 points and four assists. He ranks sixth all-time in playoff assists. For the regular season, he is 12th in all-time triple doubles and 15th in all-time assists. One does not just think one’s way to such numbers.

As for his time with the Hawks, Rondo said, “I’m not going to be a starter; I’m not coming to play 30 minutes a night. Whatever the team allows me to be and whatever they need. It may be an extension of the coach the first part of the season. It varies. I’m willing to bend either way. If I have to play a lot of minutes or if I don’t, I’ll be ready.”

The Hawks believe they have acquired someone uniquely gifted at making those around him better. And they all, from the locker room to the coaches’ offices, had best not lose concentration.

So, stay alert, Trae Young.

“I can’t wait to get in the film room with him and study his mind and have him understand the best way to attack defensive breakdowns or how defenses are trying to control and contain him,” Rondo said. “I look forward to learning from him, what he thinks and how he sees the game. I look forward to giving him a lot of input on how to destroy defenses and take his game to another level.”

The man brings some relentless plans.

“I’m never willing to give up on anybody who’s on my side,” he said.