Nadal, the No. 3 seed this year and two-time defending champion, was a four-set winner over Djokovic in the 2012 men's singles finals. The draw this year has them potentially playing in the semifinals and the wins Monday put them each one win away from that meeting.
Djokovic, the world No. 1, lost a set for the first time in the tournament before dismissing 16th-seeded Philipp Kohlschreiber 4-6, 6-3, 6-4, 6-4.
Kohlschreiber rushed out on top Monday with the only break of the first set but he went 0-for-8 in break opportunities over the second and third sets. Djokovic recorded two breaks in the final set to advance.
Nadal, marking his 27th birthday Monday, kept his record against Kei Nishikori perfect at 5-0 with a 6-4, 6-1, 6-3 victory. The 57-minute romp was Nadal's first end-to-end sharp performance of the tournament. Nishikori managed four break chances but failed to convert any of them as Nadal took 71 percent of the points on serve.
Djokovic next goes against 12th-seeded Tommy Haas, who rebounded from Saturday's 4 1/2-hour, five-set battle with John Isner with a 6-1, 6-1, 6-3 decision over No. 29-seeded Mikhail Youzhny in less than 1 1/2 hours.
Nadal's quarterfinal opponent is ninth-seeded Stanislas Wawrinka, who staged a spirited comeback in edging No. 7-seeded Richard Gasquet 6-7 (5-7), 4-6, 6-4, 7-5, 8-6 in more than 4 hours. Wawrinka dropped serve just twice in the match.
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UPI Sports Results for September 19, 2014