The No. 1 ranking could change hands next week, with Novak Djokovic reaching the top spot if he wins the title in Madrid and Rafael Nadal loses before the quarterfinals.
Nadal, who has 12,900 ranking points, won the title last year and has 1,000 points to defend. Djokovic, with 11,040 points, has only 10 points to defend after falling in the second round to Grigor Dimitrov last year. If Djokovic wins the title, he will be at 12,030 points, while Nadal will be at 11,990 points if he wins less than two matches, according to ATP calculations.
Nadal took over the No. 1 ranking from Djokovic in October.
Even if Djokovic does not reach No. 1 next week, the more matches he wins the more he will gain on Nadal, who cannot add to his total at Madrid. The Spaniard will be in a similar situation at Rome and the French Open, where he is also the defending champion.
After dominating the European clay events for years, Nadal has lost in the quarterfinals of his first two events this year, at Monte Carlo and Barcelona. Djokovic, meanwhile, enters Madrid after suffering a wrist injury at Monte Carlo two weeks ago.