There's a not-so-outlandish scenario in which Novak Djokovic would take over the No. 1 ranking from Rafael Nadal as early as Monday. It would be the first time that somebody besides Roger Federer or Nadal would sit atop the rankings since Feb. 2, 2004, a run of 380 weeks.
Here's how it would have to go down: Djokovic would have to win the Italian Open and Nadal would need to lose before the semifinals. In that scenario, Nole would gain 1,000 rankings points for a total of 11,665. (Because he didn't play the tournament last year, he isn't defending any points in Rome.) Rafa would lose 820 points because he won the event in 2010. That would give him 11,650 total, 15 fewer than Djokovic.
The first part of that scenario is a fair bet. Djokovic hasn't lost this year and recently beat Nadal on the clay courts in Madrid. The second part is what's unlikely. There have only been two occasions in the past six years where Nadal has been ousted from a clay court tournament before the semifinals. Though one of those did come three years ago in Rome when Rafa lost in his opening round, his earliest exit ever from a clay court event, that was an injury-related loss more than anything. In short, don't expect to see a change at the top before the French Open.
And though it seems inevitable that the Djokovic freight train will continue to barrel through the rankings, it's not assured that he'll get to No. 1 this year, despite his hot start. It's true that Nadal is seemingly defending every rankings point out there this summer (6,000 alone from the Grand Slams, the maximum) and that Djokovic has ground to make up, particularly at the French where he's only defending quarterfinal points. But all it takes is Rafa holding serve in Paris and then winning Wimbledon to put himself back in the driver's seat for the year-end No. 1.
For as comfortable as Djokovic seems right now in his quest for the top, that's how safe Nadal was five months ago when it was all but written that he'd cruise through the year to finish at No. 1. Things have a habit of changing quickly in tennis. Novak Djokovic won the first part of the battle. The war is far from over.