Top seed Nadal looking to step up his game

Top seed Rafael Nadal looks to step up a gear at the U.S. Open when he plays Serbian Viktor Troicki in the third round on Saturday.

The Spaniard, bidding for his third grand slam title of the year, has not dropped a set in his opening two matches at Flushing Meadows but said he would need to be on guard against world number 71 Troicki.

"I have to improve for my next round and now I have a tough opponent," Nadal said.

"I play against Troicki. He's a good server and he's playing well. I know I have to play well for try to beat him."

Fourth seed David Ferrer, who beat Nadal on his way to the semi-finals last year, plays rising Japanese player Kei Nishikori in another third-round match.

Sixth seed Andy Murray of Britain and American ninth seed James Blake are other notable names in action.

In the women's event, Wimbledon champion Venus Williams and sister Serena bid to move a step closer to a quarter-final clash when they play their third-round matches.

Seventh seed Venus opens proceedings on Arthur Ashe Stadium when she takes on Ukrainian 27th seed Alona Bondarenko, while fourth seed Serena faces Japanese 30th seed Ai Sugiyama.

And France's Julie Coin, who ousted world number one Ana Ivanovic in the previous round, faces former world number one and compatriot Amelie Mauresmo for a place in the last 16.