Andy Roddick concedes he may never win Wimbledon after crashing out along with women's second seed Vera Zvonareva crashed out of Wimbledon as Maria Sharapova survived a gutsy challenge from British 17-year-old Laura Robson. Eighth seed Roddick, beloved by the Wimbledon crowd after his epic 2009 final defeat by Roger Federer, looked a shadow of his former self in a 7-6 (7/2), 7-6 (7/2), 6-4 loss to Spanish serve-and-volleyer Feliciano Lopez. With age no longer on the 28-year-old's side, he concedes it has occurred to him that he may never get to lift the championship trophy. "Well, sure. You're human. I mean, of course it does. You may never get your favourite job either," Roddick said. "I haven't played well this year for sure. I don't think I've played my best since probably April of last year. "You keep moving forward until you decide to stop. At this point I've not decided to stop so I'll keep moving forward." Roddick had won all seven of his previous meetings with Lopez, but the Spaniard, twice a quarter-finalist, served brilliantly and stopped Roddick establishing his all-consuming power game. The world number 44's reward is a clash against either French ninth seed Gael Monfils or Lukasz Kubot of Poland for a quarter-final place. That match was one of six unable to be completed because of heavy rain that fell from late afternoon. Roddick, 28, has now failed to get past the fourth round in three of his last four visits to Wimbledon. "He played well. I got beat. He served about as well as someone has," said Roddick, who watched 57 winners speed past him on Centre Court. "The stuff that's enabled me to beat him seven times, making passing shots under duress, making him play defence on his forehand, he did well today." Lopez, who committed just seven unforced errors and out-aced the American 28-23, was overjoyed by his shock win. "It's probably the best win of my career," said Lopez, who could face Roddick again in two weeks' time when the USA take on Spain in the Davis Cup. British fourth seed Andy Murray reached the last 16 with a nervy 6-4, 4-6, 6-1, 7-6 (7/4) win over Croatia's Ivan Ljubicic under the Centre Court roof. World number four Murray will face French 17th seed Richard Gasquet on Monday for a place in the quarter-finals. The 24-year-old Scotsman, looking to become the first British men's champion since Fred Perry in 1936, overcame second- and fourth-set wobbles against the tournament's oldest player to secure his place in the second week. "It's very intense here -- I just need to serve better, but I returned well and I'm ready. I thought tonight's match was a very, very high standard," said Murray. World number two Zvonareva was consigned to the exit when she slumped to a 6-2, 6-3 defeat against Bulgaria's Tsvetana Pironkova, the woman she beat in the semi-finals in 2010. Pironkova next faces five-time winner Venus Williams, a year after beating the American 23rd seed in the quarter-finals. Williams reached the last 16 with a 6-0, 6-2 mauling of Spain's Maria Jose Martinez Sanchez. Williams said she would not let anything get in her way as she tries to dish up a stone-cold dose of revenge on Pironkova. "Last year, unfortunately I didn't play that well. I don't feel I competed well. Regardless of how I play, I know I'll be competing this time," the 23rd seed said. "I'm ready to bring my best game and my best competition. Last year I just got unhappy with how I was playing and I let that affect my game. This year I won't let that happen. Sharapova, the fifth seed, recovered from 4-1 down in the first set to reach the third round with a 7-6 (7/4), 6-3 win over Robson, playing on a wildcard and ranked at 254 in the world. The 2004 champion will face Klara Zakopalova of the Czech Republic for a place in the last 16 on Saturday. "She started so well. She was going for her shots and serving so well that I couldn't get too many looks on her first serve," said Sharapova. "But I played better as the match went on." Top seed Caroline Wozniacki eased into the third round playing on the same Court Two that had sparked Serena Williams's bitter accusations of favouritism 24 hours earlier. World number one Wozniacki defeated France's Virginie Razzano 6-1, 6-3 in a second round match held over from Thursday and next faces Australia's Jarmila Gajdosova for a last-16 place. Russian 12th seed Svetlana Kuznetsova was a third-round loser, with the former US Open and French Open champion slipping to a 4-6, 6-3, 6-4 defeat by Belgian 19th seed Yanina Wickmayer. German 11th seed Andrea Petkovic also fell, losing 6-4, 7-6 (7/2) to Russia's Ksenia Pervak, but eighth-seeded Czech Petra Kvitova, a semi-finalist in 2010, eased past Roberta Vinci of Italy 6-3, 6-3. Heavy rain meant that defending champion Rafael Nadal will have to come back on Saturday to complete his third-round match with Luxembourg's Gilles Muller. The top seed was 7-6 (8/6) ahead when play was abandoned for the day. He could face former US Open champion Juan Martin Del Potro in the next round. The 24th-seeded Argentine was leading France's Gilles Simon 7-6 (10/8), 2-4 when play was halted.