Nishikori survives second round scare

World number five Kei Nishikori survived a gruelling second round match against Australia's James Duckworth to advance to the third round of the Citi Open. 

Both men dropped their serve twice in the opening set, before Duckworth saved one set point before edging a tight tie-break 10-8 to take the 

However, Nishikori, who was playing in his first match since withdrawing from Wimbledon prior to the second round due to a calf injury, came roaring back to win the second set 6-1 in just 29 minutes. The 25-year-old never looked back, claiming the lone break of serve in the decider to trump Duckworth 6-7 (8), 6-1, 6-4 in two hours and 19 minutes. 

Nishikori will either face 16th seed Leonardo Mayer or Blaz Rola in the third round. 

Twelfth seed Vasek Pospisil won his second round match against Donald Young 7-5, 6-3 and will be joined in the next round by 13th seed Sam Querrey, who beat Japan's Go Soeda 6-3, 5-7, 6-4, and 15th seed Jack Sock, who downed Ruben Bemelmans 7-6 (7), 6-3. 

Earlier in the day, Lleyton Hewitt, Sam Groth, Tim Smyczek, Guido Pella, Steve Johnson, Gilles Muller and Blaz Rola all won their first round matches.