But put him on the floor with the best of his countrymen, taking on the best of the rest of the world, and that confidence fizzles.
Rondo withdrew from consideration for USA Basketball on Tuesday, making coach Mike Krzyzewski's job easy as he whittles his roster down to 12 players for the upcoming FIBA World Championship.
The Celtics' 24-year-old point guard was seen by many as a strong candidate to start for Team USA at Worlds, but his status has taken a free fall over the course of the last week. First, he lost his starting job to Derrick Rose; then he was kept out of Sunday's exhibition game against Spain.
"I think I'm on the bubble," Rondo said Tuesday to ESPN's Chris Sheridan. "Just looking at the obvious — I got a DNP last game. That pretty much speaks for itself."
Then he popped the bubble himself.
It's strange, because Rondo's always believed in himself, and it's not like him to back away from a challenge, especially when he's got the chance to take on the world's best.
But maybe Rondo, despite all his physical gifts and all his abilities on the court, wasn't the best fit for Team USA. Coach K seemed to imply that with his comments after Rondo's DNP, in which the Americans narrowly beat the Spaniards, 86-85.
"It's not so much what Rajon has to show, it's what our team needs," the coach said. "We've found a good lineup, and the international game is so different from the NBA game, you can ask any of these guys. Part of it is to make sure that we try not to have two non-shooters out on the court, and there's the physicality, too.
"Derrick right now being with Chauncey [Billups] is a good [combination], and Stephen [Curry], he provides a different thing, because if they are going under [screens] and they keep going under on him, then he has a 3. So it forces another team to change the way they defend our team. So it's things like that, and how we feel strategy-wise what'll be best for the team."
Rondo's an NBA champion, he's an All-Star, he's first-team All-Defense, and he's got a new $55 million contract. But this experience will help him see his shortcomings.
He isn't big and strong. He isn't the same playmaker in the halfcourt that Rose and Billups can be. And he's not a deadly shooter by any stretch of the imagination.
Simply put, he's probably not fit for the international game.
No doubt, this realization sank in for Rondo at some point this week — first on Saturday against Lithuania, when he recorded just two points, one assist and four turnovers, and then against Spain as he watched Rose and Billups take on Ricky Rubio. This Worlds thing wasn't working out like he hoped.
So he stepped down with his pride intact. Rather than stick around with Team USA, where even if he made the team he'd be relegated to the bench, he came home on his own terms.
In a few short weeks he'll be back with his Celtics. He's not on the bubble in Boston — he's a rising superstar and he's the face of a prestigious franchise.
Rajon Rondo's confidence may have taken a small hit this week. But by the time he's back on the floor at the TD Garden, it'll all come right back. And then some.