Federer had been No. 1 for the last 11 weeks since collecting the title at Wimbledon. That championship tied him with Pete Sampras for the most weeks at No. 1 and Federer has since pushed that to 296 weeks.
The ATP schedule was open last week in favor of the Davis Cup World Group semifinals and other playoffs. Federer won a pair of matches in helping Switzerland win its playoff against the Netherlands. Davis Cup matches, however, don't figure in the world rankings.
Spain, which was paced by world No. 5 David Ferrer, will go against the Czech Republic, which boasts No. 6-ranked Tomas Berdych as its top player. The teams will meet Nov. 16-18 in the Czech Republic for the title. It is a rematch of the 2009 final, which Spain won 5-0.
Ferrer has 5,960 points and Berdych has 4,965. Jo-Wilfried Tsonga is seventh and has 4,520 points. Juan Martin del Potro is eighth with 3,850 points and Janko Tipsarevic (3,285) and John Isner (2,610) complete the Top 10.
Tsonga, the top seed and defending champion at the Moselle Open in his native France, is the only Top 10 player on this week's schedule.
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