The highest American seed was eliminated from the U.S. Open by a Frenchman.
France's Jo-Wilfried Tsonga defeated No. 8 Mardy Fish in five sets to reach the quarterfinals of the season's final Grand Slam. Tsong's 6-4, 6-7 (5), 3-6, 6-4, 6-2 victory places him in the round of eight in America for the first time in his career.
But while one seed was knocked out, another continued.
No. 1 seed Novak Djokovic had trouble in his first set, fighting off four first-set points against Alexandr Dolgopolov in the fourth round of the US Open. He eventually won the 30-point first-set tiebreaker 16-14, and the match 7-6, 6-4, 6-2. The win extended Djokovic's 2011 record to 61-2.
The No. 1 seed will face fellow Serb Janko Tipsarevic in their quarterfinal match. Tipsarevic is the tournament's 20th seed.
"There's going to be at least one Serb in the semifinals, which is great for our country," Djokovic said in a televised courtside interview. "This is the first time I play Janko in a Grand Slam. We're great friends, it's not going to be easy playing him."
Three Americans still remain in Flushing Meadows.