North Carolina coach Roy Williams revved up Dean Smith's classic secondary break to create the college game's most relentless -- and riveting -- attack

	Lawson's extra gear and ability to dart between defenders help the Tar Heels average 1.17 points per possession. David E. Klutho/SI

It was a simple exchange, really, a moment that laid bare Roy Williams's vision to create the most lethal attacking weapon in college basketball. In the fall of 2002, not long after rejoining Williams's staff at Kansas, Steve Robinson stood next to his boss during a preseason practice and blanched at the scene before him, a chaotic blur of bodies in motion. The Jayhawks hadn't operated this way seven years earlier, when Robinson had left to coach Tulsa (and later Florida State). "I'm a little uncomfortable with how fast you're playing," Robinson told Williams, who cackled like a mad scientist. "Good," Williams replied. "Because I want to play even faster."

In today's game Ol' Roy's ongoing metamorphosis

is nothing less than revolutionary. Whether it's for reasons of ego or control or changing personnel, most Hall of Fame-worthy coaches have slowed down their attacks over the past two decades. Consider Pat Riley, who's gone from running the Showtime Lakers to the bump-and-grind Miami Heat, or Louisville's Rick Pitino, who almost never uses the full-court press he made famous at Kentucky. "Some guys are trying to go slower than they used to, but I'm always trying to go faster," says Williams. "Basketball is supposed to be a finesse game -- Dr. Naismith didn't want people to foul each other -- and I think speed is a part of finesse."

Structured chaos, Williams calls his brainchild, an ever-quickening version of his mentor Dean Smith's classic primary and secondary breaks. It sounds like an oxymoron until you see the uncanny way in which Williams's latest North Carolina team mixes the supposedly competing elements of breakneck speed and wise shot selection. With a month to go before the NCAA tournament, the Tar Heels (23-4 through Sunday) own the most fear-inducing offense in the land, not least because they're the country's fastest-paced major-conference team (averaging 75.1 possessions a game, according to kenpom.com) and ranked No. 4 nationally in offensive efficiency, scoring 1.17 points per possession. We've seen this deadly combination before, of course: In both categories the Runnin' Heels are neck and neck with Williams's 2005 national champs.

The Carolina break is more dangerous than ever because the Tar Heels have uncommon depth, rotating as many as 12 players, none of whom ever stops running. If UNC has a numerical edge and can score on a traditional fast break, a.k.a. the primary break, then that's the first option after a make or a miss by an opponent. If not, the Tar Heels will launch into their secondary break, a term that many hoops fans have heard but only a few understand. "The secondary break is the phase between the primary break and a set offense," Williams explains. "It gives us a chance to keep attacking so that defenders have to pick up people they're not supposed to be guarding. They're backpedaling and trying to protect the goal, and now we're moving it around and setting screens before the defense can really get set."

Sports Illustrated senior writer Grant Wahl covers college basketball for the magazine and SI.com.