Rafael Nadal's irrepressible form continued as he thrashed Brazilian qualifier Rogerio Dutra Silva to move into round three of the US Open.The world number two, who has won nine of his 12 tournaments this year and all 21 hard court matches, outclassed Dutra Silva 6-2 6-1 6-0 in 92 minutes.Defending champion Serena Williams, five-time winner Roger Federer and second seed Victoria Azarenka also won.But fourth seed Sara Errani was eliminated by Flavia Pennetta.Arthur Ashe StadiumFlavia Pennetta (Ita) bt Sara Errani (Ita) [4] 6-3 6-1Fourth seed Errani admitted she felt so weighed down by pressure that she did not want to go on the court before losing to her compatriot.Maria Sharapova's withdrawal meant the 26-year-old was elevated to fourth seed and she struggled to cope with it."I think it's the pressure," said a tearful Errani. "I have never been in this situation. I don't want to go on the court. I don't want to go to play. I don't want to stay there on the court. I feel very bad."Serena Williams (US) [1] bt Galina Voskoboeva (Kaz) 6-3 6-0The 16-time Grand Slam champion needed just 69 minutes to book a third-round meeting with Yaroslava Shvedova, of Kazakhstan, and has now lost only four games in two matches.Roger Federer (Swi) [7] bt Carlos Berlocq (Arg) 6-3 6-2 6-1"It might take a few matches and next thing you know you're playing really, really good tennis again and you're close to playing some really great tennis," said Federer, who is at his lowest world ranking - seventh - since 2002."I think that's kind of where I am right now, and that's where every match is really important to me and how I play every single point."Caroline Wozniacki (Den) [6] bt Chanelle Scheepers (RSA) 6-1 6-2Rafael Nadal (Spa) [2] bt Rogerio Dutra Silva (Bra) 6-2 6-1 6-0Nadal showed no sign of the injuries that have plagued him over the past two years and later said: "I'm trying to play more aggressive."I didn't have time to practise a lot because I was injured for seven months and when I started to feel better I started to compete. I need to play more aggressive - I'm trying to work on this my whole career but it's more mental than a training thing." Louis Armstrong StadiumAngelique Kerber (Ger) [8] bt Eugenie Bouchard (Can) 6-4 2-6 6-3Bouchard, 19, has been tipped as a future star, but Kerber battled through and remains on course for a quarter-final meeting with Serena Williams.David Ferrer (Spa) [4] bt Roberto Bautista Agut (Spa) 6-3 6-7 (5-7) 6-1 6-2His pre-tournament form was unimpressive, but Ferrer has now made it to round three or better at each of the last 15 Grand Slams.Victoria Azarenka (Blr) [2] bt Aleksandra Wozniak (Can) 6-3 6-1Azarenka, who beat Serena Williams at the recent Cincinnati Open, was broken three times on a windy day - but she prevailed in a little over an hour to book a meeting with Alize Cornet of France.John Isner (US) [13] bt Gael Monfils (Fra) 7-5 6-2 4-6 7-6 (7-4)Number 13 seed Isner held off Monfils to progress as the last-seeded American in the men's draw, despite the Frenchman getting more than his share of support in front of Isner's home crowd. GrandstandAna Ivanovic (Ser) [13] bt Alexandra Dulgheru (Rom) 6-2 6-1Adrian Mannarino (Fra) bt Sam Querrey (US) [26] 7-6 (7-4) 7-6 (7-5) 6-7 (5-7) 6-2Mannarino is through to round three of a Grand Slam for only the second time, and his reward is a meeting with Roger Federer.Querrey's first defeat before round three at Flushing Meadows since 2007 means the highest-ranked US man left in the draw is 13th seed Isner. Brits abroadDan Evans (GB) bt Bernard Tomic (Aus) 1-6 6-3 7-6 (7-4) 6-3Match reportJamie Murray (GB) and John Peers (Aus) bt Fernando Verdasco (Spa) [9] David Marrero (Spa) [9] 7-6 (7-4) 6-4Britain's Murray and his Australian partner Peers will continue their doubles bid against Feliciano Lopez and Andre Sa after an impressive 81-minute victory over ninth seeds Verdasco and Marrero.Dominic Inglot (GB) [16] and Treat Huey (Phi) [16] bt Jurgen Melzer (Aut) and Julian Knowle (Aut) 6-2 6-7 (4-7) 7-6 (7-5)Jiri Vesely (Cze) and Jaroslav Levinsky (Cze) bt Ken Skupski (GB) and Denis Istomin (Uzb) 6-3 6-3 Outside courtsPetra Kvitova (Cze) [7] bt Bojana Jovanovski (Ser) 6-2 6-4Richard Gasquet (Fra) [8] bt Stephane Robert (Fra) 6-3 7-5 7-5Tommy Robredo (Spa) [19] bt Frank Dancevic (Can) 6-4 6-4 6-1The 31-year-old former world number five looked hugely impressive as he knocked out Dancevic to set up a meeting with Britain's Dan Evans.