Five-time champion Serena Williams reached her first Grand Slam quarter-final of 2014 at the US Open but Canadian poster girl Eugenie Bouchard, struggling in the heat and humidity, was knocked out. World number one Williams, the two-time defending champion, eased past world number 50 Kaia Kanepi 6-3, 6-3 on Monday for a fourth win over the Estonian and goes on to face fellow 32-year-old Flavia Pennetta of Italy in a clash of the two oldest remaining players in the draw. "It's my first quarter-final of the year at the majors -- at last I did it," said the American, who had fallen in the fourth round in Australia, the third round at Wimbledon and suffered a second round French Open exit. Seventh seeded Bouchard was at the centre of a medical drama on Louis Armstrong court when she had to have her blood pressure and temperature taken in her 7-6 (7/2), 6-4 defeat to Russian 17th seed Ekaterina Makarova.
Former champions Novak Djokovic and Andy Murray booked a tantalizing US Open quarter-final duel with straight-sets fourth-round victories. World number one and top seed Djokovic didn't let Philipp Kohlschreiber stand in the way of another Grand Slam last-eight appearance on Monday, defeating the 22nd seed from Germany 6-1, 7-5, 6-4 on another oppressively muggy New York day. Eighth-seeded Scot Murray advanced with a hard-fought 7-5, 7-5, 6-4 victory over ninth-seeded Jo-Wilfried Tsonga, avenging a loss to the Frenchman in the Toronto Masters last month. They are 2-2 in Grand Slam finals, including Murray's triumph over Djokovic in the 2012 final at Flushing Meadows for his first major crown.