Serena Williams and Ekaterina Makarova sprinted into the semifinals of the U.S. Open Wednesday, while world No. 1 Novak Djokovic and marathon man Kei Nishikori were forced to take the long road into the last four.

Having already played the longest match of the tournament in the fourth round, a bruising four-hour 19-minute battle with Canadian Milos Raonic, Nishikori had enough left in the tank to get past third seed Stan Wawrinka 3-6, 7-5, 7-6 (7), 6-7 (5), 6-4 in a 4-hour 15-minute test of wills to become the first Japanese man into the last four of a Grand Slam in 81 years.

While Murray and Djokovic battled their way through a 73 minute opening set, 32-year-old Williams needed just 63 minutes in total on a sultry evening to breeze past Italian Flavia Pennetta 6-3, 6-2 and became the oldest player to reach the last four at Flushing Meadows since Martina Navratilova in 1991 .

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