After seven years, four coaches, and two general managers, the rebuilding is finally complete.

The Chicago Bulls ended one of the most enduring runs of incompetence in basketball history this week by clinching their first playoff berth since Michael Jordan walked away after the 1997-98 season. Until now, the post-Jordan era in Chicago has been utterly forgettable. The team never won more than 30 games in a season and in many years didn’t even come close.

That said, this season has been an unbelievable turnaround. Not only will the Bulls appear in the playoffs, they’ll have home-court advantage for the first round. If they run the table in the final six games of the regular season, the Bulls could do the unthinkable and win 50 games.

All that seemed impossible when the team began the season 2-13. With a young team that lacked star power, Chicago fans seemed resigned to another year of nightly beatings. But they’re 42-19 since then, which is a 56-win pace over a full season.

How is this possible? Chicago’s lineup isn’t exactly crawling with superstars – or even minor stars. Take a look at the league leaders in Player Efficiency Rating (PER), my per-minute ranking of a player’s statistical production. The highest-rated Bull is Tyson Chandler at 16.46. That mark barely exceeds the league average and ranks 80th in the NBA overall. In other words, 79 players are putting up better numbers than anybody on the Bulls.

Considering those numbers, it won’t surprise you to learn that Chicago’s offense is nearly as anemic as the Nets’. The Bulls rank 26th in Offensive Efficiency, my measure of a team’s offensive output, with an average of 98.04 points per 100 possessions (the Nets rank 28th at 97.48).The teams have different types of offenses – the Nets have two good players surrounded by several awful ones, while the Bulls are just mediocre all over. But the net effect is the same.

Despite the shoddy offense, the Bulls are able to win because of their fantastic defense. Chicago’s excellence in this area has been partially masked by the team’s relatively fast pace. Notwithstanding their reputation as a tough, physical team in the gritty mold of coach Scott Skiles, the Bulls like to run, clocking in with the league’s 10th-fastest pace at 95.1 possessions per game.

Because of the pace, the Bulls’ defense doesn’t get enough credit. Chicago allows 93.7 points per game, which ranks fifth in the league. We tend to look at that and think, “Good but not great.” That’s especially true when one compares it to the Detroit Pistons, who give up just 89.9. But here’s the kicker: the Bulls’ defense has been every bit as good as the defending champions’ – which they showed during last night’s 85-84 loss to Detroit. This is the secret to how Chicago can win so often without getting much help from the offense.

The Bulls lead the NBA in opponent field-goal percentage, allowing a 42.3% success rate, which is a full percentage point lower than Detroit’s. Overall, Chicago gives up 97.82 points per 100 possessions, ranking within a micron of Detroit’s 97.81 and placing them third overall in the league.

Look at Chicago’s lineup again and the defensive excellence is puzzling. The starting center, Eddy Curry, is primarily an offensive player whose poor conditioning and inattention to help defense frequently relegate him to the bench in the fourth quarter. Moreover, two of the Bulls’ other starters are rookies, a group that usually struggles at the defensive end.

But in this case, the rookie stereotype isn’t true. The two newbies, Chris Duhon and Luol Deng, have been able to contribute immediately on defense. Duhon, in fact, could best be described as the Bulls’ Jacque Vaughn – he’s dead weight on offense but shuts down opposing point guards. Deng has been solid as well, with good quickness, size, and surprising strength for a teenage rookie, though he’ll miss the rest of the season with a wrist injury.

Additionally, the rest of the Bulls are outstanding defenders. Power forward Antonio Davis is as strong as any player in the league and happily takes charges on penetrating guards. Davis’s backup, ex-Knick Othella Harrington, is tormenting the folks at the Garden by having a completely unexpected career year. In the backcourt, Kirk Hinrich is vastly underrated at the defensive end, moving his feet well and contesting shots all over the court.

The Bulls haven’t lost any steam with Deng out. His replacement has been The Wild Bull of the Pampas, Argentine import Andres Nocioni. He’s a tough defender who routinely pushes the envelope with his physical play, and his bug-eyed expressions only add to the spectacle.

Because of the rough tactics, Nocioni edges out Seattle’s Danny Fortson for “player most likely to have a bounty put on him by an opposing coach.” Amazingly, it took 70 games for somebody to take a swing at him, but Miami’s Udonis Haslem finally ended the streak last week by clocking him after Nocioni’s hard foul on Dwyane Wade.

One Bull, however, stands out more than any at the defensive end: Tyson Chandler. Chicago’s backup center rarely starts games but usually finishes them, and his length and energy are infectious. As good as Chicago is for all 48 minutes, they really slam the door when Chandler enters, allowing 2.2 fewer points per 48 minutes when he’s on the floor.

The key to his game is his ability to block and alter shots without getting out of position. He averages 2.5 blocks per 40 minutes but rarely takes a bad gamble going for blocks he can’t reach. Chandler has also grown into a ferocious rebounder; his average of 14.2 rebounds per 40 minutes ranks fifth in the NBA. Combine that with the lateral movement to switch out and guard smaller players, and he’s a Defensive Player of the Year in the making.

Chandler won’t win that honor this year, but he’d be a deserving winner of the Sixth Man award. Teammate Ben Gordon has been hyped for that honor, but Chandler has played more minutes, has better overall statistics, and has been the prime contributor to the Bulls’ most important element: the defense.

But the true catalyst for Chicago’s resurgence has been Skiles. When he took over the Bulls, they rarely played hard and were porous defensively. In a little over a year, he’s made the team one of the best in the East by molding his players into clones of his old playing self: tough, uncompromising, and hungry. By adopting the coach’s attitude, the Bulls have managed to overcome a seemingly huge talent deficit.

Between the players’ outstanding efforts and the coach’s willpower, it’s been a remarkable transformation for the Bulls. Best of all, it shows little sign of abating. As I mentioned, most of the key players are still very young and should be linchpins of Chicago playoff teams for the foreseeable future. It took them long enough, but the Bulls finally have a winner again.