At the Net: Djokovic turns up the heat on Nadal

Philadelphia, PA ( - Novak Djokovic could reclaim the No. 1 ranking from Rafael Nadal in the coming weeks. The top-two players on the planet have forged quite the rivalry in recent years and will duel on the European red clay over the next two months to decide the top dog.

The six-time Grand Slam champion Djokovic cannot return to No. 1 next week in Monte Carlo, where he's the defending champion after ending Nadal's incredible eight-year reign there a year ago.

There is, however, a possibility that Nole could unseat the mighty Spaniard as early as mid-May following the Madrid Open.

During the eight-week European clay-court swing, Nadal will have to defend over 3,000 points more than Djokovic, whom he currently leads by just over 2,000 points in the rolling 52-week ATP rankings.

The 13-time major champ Nadal, of course, was unreal on the dirt last year, claiming titles in Barcelona, Madrid, Rome and at Roland Garros, and needs to defend 5,100 points. Though Djokovic came out on top in Monte Carlo and reached the French Open semifinals, he suffered a second-round upset in Madrid and was upended in the quarterfinals in Rome, which leaves him having to defend just 1,910 points.

Note: Points earned at a tournament stay on a player's ranking for 52 weeks before dropping off.

The amazing Nadal, who has titled in Doha and Rio and been a runner-up in Melbourne and Miami in 2014, has held the No. 1 ranking for 129 weeks during his wonderful career, reclaiming the top spot last year after a brilliant comeback to the ATP circuit. After being sidelined for seven months with a left knee injury, Rafa returned to capture five Masters 1000 titles and a pair of Grand Slam championships before overtaking Djokovic in October.

After going without a title through the first two months of a season for the first time since 2006, Djokovic hit his stride (and then some) recently to corral the Indian Wells-Miami double for the second time in four years to close the gap on Nadal to 2,050 points at the top. The Belgrade native finished 2013 as the player to beat, winning four straight titles in Beijing, Shanghai, Paris and London, at the elite ATP World Tour Finals.

Note: Nadal and Djokovic are two of the top-three all-time prize money leaders (Roger Federer is No. 1).

Djokovic, who himself has spent 101 weeks at No. 1 during his career, and the Aussie Open runner-up Nadal rekindled their outstanding rivalry two weeks ago in the finale in Miami, with the Serb prevailing in straight sets in the 40th installment of the head-to-head series. Djokovic has won the last three meetings, but Nadal still leads the lifetime set, 22-18.

Just for the record, when it comes to clay, Nadal is the undisputed king.

The Spanish bull boasts a brilliant .934 winning percentage and 298-21 record on the stuff. Only two other players have a winning percentage over .800, and they are Bjorn Borg (.863) and Ivan Lendl (.814). Djokovic is Rafa's closest contemporary with a .774 mark.

Outside of Federer, only two other players have beaten Nadal in a clay-court final, with Djokovic doing it three times at Masters events, and Horacio Zeballos (who?) accomplishing the stunning feat last year in Nadal's comeback tournament in Vina del Mar, Chile.