Nishikori forced to dig deep

Fourth seed Kei Nishikori survived a fightback to see off Sam Querrey in the second round of the Citi Open in Washington.

The 24-year-old world number 11 from Japan, took the first set 6-4 before his American opponent hit back to take the second 7-5, but 2012 Australian Open quarter-finalist Nishikori advanced following a 6-4 win in the third in an hour and 52 minutes on Stadium Court.

Top seeds Tomas Berdych and Milos Raonic recorded straight-sets victories to Nishikori in the next round.

No 1 seed Berdych defeated Robby Ginepri 6-1 6-4, while second-seeded Raonic battled past Jack Sock 7-6 (7-3) 7-6 (7-3).

Sixth seeded Richard Gasquet also enjoyed a comfortable win as the Frenchman brushed past Dudi Sela 6-3 6-2, while Santiago Giraldo, ranked 10, overcame Benjamin Becker 6-2 7-6 (7-3) and 13th seed Vasek Pospisil edged out. Rajeev Ram 6-0 7-6 (10-8).

Home hope Donald Young, though, caused an upset with a 6-4 6-3 victory over 17th seed Julien Benneteau of France in the opening match on Court 1 to set up a third-round tie against compatriot Tim Smyczek.

Eighth seed Feliciano Lopez of Spain was also knocked out as he suffered a straight-sets defeat to Victor Estrella.

The world number 24 made his exit after he lost 7-6 6-4 to his opponent from the Dominican Republic in an hour and 18 minutes.