Rondo does some things every night that surprise even himself. (Photo by Brian Babineau/Getty Images)

When Rajon Rondo is on top of his game, everything comes down to yo-yo’s.

The game’s like a yo-yo in his hands. The ball’s like a yo-yo in his fingertips. He can walk the dog, put it around the world, even rock the baby. When Rondo’s yo-yo’ing around, the game is his. Everyone else is too slow. No opponent can keep up. It’s like he’s a grown man on a playground with little kids, only the little kids are all taller and stronger than he. But they aren’t faster, they don’t have better court vision, and they aren’t in control. They don’t have the game at their fingertips. Not like Rondo does.

“I would just take Rondo,” Doc Rivers said when asked who he’d choose if he had his choice of one point guard. “I wouldn’t even look at another point guard. There are some great point guards in the league, we’ve seen a couple of them the last two games, in Deron Williams and Chauncey Billups. But we have Rondo and he’s my guy.”

It hasn’t always been that way. Three seasons ago, he backed up Sebastian Telfair as Boston stumbled to a 24-58 season. Even two seasons ago, Rondo was the weak link in the Celtics’ starting five. Sam Cassell was signed midway through the season as a backup point guard, and the hope was that Cassell would play well enough to supplant Rondo as an end-of-game option. It didn’t work out. Cassell flopped, launching brick after brick, losing Doc’s confidence along the way. But that didn’t mean Rondo’s job of closing out games was safe. When push came to shove, and the Celtics needed to close out playoff wins, Eddie House often heard his number called.

Last season was different. Rondo emerged as one of the league’s up-and-coming stars with a breakout postseason. Paired against Rookie of the Year Derrick Rose and then a hungry Orlando defense, Rondo alerted the world what he’s always believed, in that self-confident heart of his: Number Nine will eat you alive. He dropped 16.9 points, 9.8 assists, and 9.7 rebounds per game, as he wrestled control of the Celtics from the two Big Three members standing. It wasn’t so much that there was a struggle for power, so much that Rondo seized it with little resistance. The conch was his, and he earned it the right way: By outplaying whatever opponent stood in front of him.

But there were rumbles of discontent. Rondo was fined for being late to a playoff game. He was labeled a troublemaker in the locker room, a disruptive force. “We need him to be more of a leader,” said Danny Ainge at the time. “He’s got to grow up in some cases.” Bob Ryan wrote, “He’s not some awful person, but let’s just say he has his ways, and he sometimes grates on teammates, coaching staff, and management.” Part of the solution on the floor, Rondo was deemed a problem off it.

Ainge looked into trading the young star in the offseason. His name was involved in rumors with the Detroit Pistons and Memphis Grizzlies, among other teams. Less than two months after being a nightly triple-double, Rondo was unsure if he’d ever play another game as a Celtic.

Not that it affected his preparation. After draft night passed and Ainge hadn’t pulled the trigger on any trades, it became clear that Rondo would stay with the only NBA organization he’d ever played for. Did he harbor grudges? Not on the surface, at least. Instead of pouting during the offseason, Rondo put on 11 pounds of muscle. Rather than fire back at Danny Ainge and Doc Rivers verbally, Rondo kept his mouth shut and returned to camp a different player. Scratch that, a different teammate. Where others might have rebelled at the criticisms, Rondo took them to heart. He changed his ways. He remodeled himself to be better for his team.

And it showed on the court. From day one this season, Rondo has been the Celtics’ leader. With his play, with his words, everything. “It’s weird,” Nate Robinson said of Rondo’s role on the team. “You’ve got Rondo running the show, you’ve got KG, and he’s a vet. It’s like you got a guy out here, young guy, running the show, and the vets and everybody are just listening and just try to play together.” The team that tried to get rid of him, now listening to his orders. The locker room he once disrupted, heeding his advice.

Boston rewarded his new attitude and improved play with a 5-year, $55 million contract extension. The NBA recognized him as an All-Star. He just broke Rick Fox’s Celtics single-season record for steals, and will soon erase Bob Cousy’s Celtics single-season assists record. With those two records, Rondo’s evolving maturity, and elite rebounding rarely seen from a point guard, Rondo’s season is one of the best a point guard has compiled in the Celtics’ storied history. Right there with Cousy’s prime years.

“[Rondo has] grown up before everybody’s eyes,” said Garnett, who has always contended that Rondo could become one of the league’s top point guards. “You want your point guard setting the tone every night. You want your point guard leading [you]. It’s great to watch because I’ve seen him when he was quiet, hiding in the corner, didn’t say two words. Sometimes we sort of miss that.”

Garnett’s only kidding about missing the old Rajon Rondo, the one who used to hide in the corner, come late to games, and scrape only the surface of his vast potential. That Rondo isn’t coming back. A maturation process has left a new Rondo, a better Rondo, a Rondo prepared to carry his team into tomorrow, and lead them today.

The wild thing about his evolution, the scary part for the rest of the NBA, is that Rondo will only get better. He’s improved by leaps and bounds every year, in every aspect. Each night, the team falls a little more into his control, as he continues the process of receiving the torch from the Big Three. The Boston Celtics aren’t yet completely his, but they will be.

And when they are, the Celtics will be in good hands.

Just like the yo-yo attached to his fingertips.