It was Rondo's second season in the league, and he hadn't yet morphed into the conductor of a world-famous Celtics orchestra boasting three Hall of Famers.
That didn't fool the Garnett, though. He knew Rondo had the gift.
"After the third day when I just got here, we were doing pick up [games]," said Garnett. " You could see his potential from how he was dictating pick up games. Not so much that he was scoring the ball but he was dictating a lot of plays from both ends."
Amazing, isn't it? That was Garnett's observation after knowing the guy for three days. But after all, this wasn't an average joe talking up a teammate. This was Kevin Garnett, a time-tested veteran and former MVP.
You have to be pretty special to draw that kind of attention from Garnett.
And Rajon Rondo is.
Flip the calendar ahead five years and look at him now. Rondo has had his ups and downs -- who hasn't? -- but he has become one of the league's premier point guards.
His ability to find teammates when he's seemingly looking the other way is otherworldly. He runs an offense like no other. It's truly awe-inducing to watch, and baffling to comprehend.
Doc Rivers, a tremendous point guard back in his day, can't even fully grasp it.
"I can't," Rivers said when asked to describe Rondo's game. "It's an offense in itself."
Those words speak volumes. Just think about that for a second. Rondo's performance baffles even Rivers, a coach who many consider to be one of the top two in the league.
Some would even take it further and call him the best point man on the planet.
"It's incredible playing with Rondo," said Jason Terry. "Like I've said before, he's the best point guard in the game."
Sometimes, it's very hard to argue that. Ronda's latest show of dominance (or Rondominance, as I like to say) was his 20-assist outing in the Celtics' 107-89 win over the Toronto Raptors on Saturday. The total, one he has reached twice this season and seven times in his career, extended his streak of consecutive games with 10 or more assists to 32. He is now averaging a league-best 12.6 assists and is only 12 games away from tying Magic Johnson's record of 44 games with double-digit assists.
The magnitude of that number is enormous, and that places him in elite category with the likes of Johnson and John Stockton. Right where he belongs.
"Yeah, there's been a couple," Rivers said when asked if he has seen passing spurts like Rondo's. "Jason Kidd in his hey day, Magic (Johnson) all the time, (John) Stockton. But think about it; I've named four or five guys. The league's been around a long time. So it's not a lot, and he's one of them."
And yet if you ask Rondo what that streak means to him, he won't take the traditional route of calling it an honor or humbling.
To him, it's all about the team.
"It means my teammates are making shots," Rondo said about his lofty assists streak. "I'm making some OK passes, just taking what the defense gives me."
And that attitude is what make him so special.
Rondo may not be an all-around dominant player like LeBron James. His jump shot is still inconsistent -- the constant knock on him that has kept him from receiving the same recognition of Chris Paul, Steve Nash or Jason Kidd.
When it comes to playing the position of point guard, however, there are none better. The way he distributes the basketball and runs the Celtics offense is a thing of beauty, and that's why many, Jason Terry and myself included, would call him the best pure point guard in basketball.
Because for Rondo, it's not about him. At all. It's about the team, every second of every game. And what is a point guard if not the one who is responsible for running his team?
"He's Peyton Manning out there," said Courtney Lee. "He's picking the defense apart and he's getting the ball to guys in the right position to score."
So many all-time greats have put on the Celtic green and white, and if you don't believe me, take a look at the TD Garden rafters when you get the chance.
Someday down the road, that's where Rondo's number and legacy will remain.
"He's a rare bird," said Rivers. "I mean, he really is."
Gethin Coolbaugh is the Editor of SB Nation Boston. Twitter: @GethinCoolbaugh.