Rafael Nadal closes in on No. 1 ranking; Roger Federer rises to sixth

Rafael Nadal is poised to return to No. 1 before the year is over. (Mike Stobe/Getty Images)

Rafael Nadal has put himself in position to reclaim the No. 1 ranking for the first time since June 2011.

After his U.S. Open victory, Nadal sits only 120 points behind No. 1 Novak Djokovic in this week's rankings and has no points to defend until next February. Djokovic has 3,010 points to defend the rest of the year after winning the China Open, Shanghai Masters and ATP World Tour Finals last fall. The next scheduled ATP tournament for both men is the China Open, which begins Sept. 30.

"I'm still No. 1, but year to year he's far, far ahead, and he has much more chances to end up as No. 1," Djokovic said. "Look, there are still tournaments to go. So we'll see."

In other rankings news, Roger Federer moved up one spot, to No. 6, thanks to Juan Martin del Potro's second-round loss to Lleyton Hewitt in the U.S. Open; the Argentine fell from sixth to seventh. Federer's next scheduled event is Shanghai, which starts Oct. 6.

One concern for Federer is whether he'll qualify for the World Tour Finals in London. Only the top eight players, based on points earned in 2013, qualify for the season-ending tournament, which Federer has played the last 11 years and won six times. The Swiss is seventh in the Race to London. His primary threats are his countryman Stanislas Wawrinka, who trails by only 130 points, and Richard Gasquet, who is 290 points behind.