SHANGHAI (AFP) Chinas unfancied outsider Zeng Shao Xuan sprang the first surprise of the new Shanghai Masters Sunday, with the number 396 winning the first ATP-level match of his life to reach the second round. The underdog put out Israeli Davis Cup player Dudi Sela, holding his nerve in the final set to take a 2-6, 6-1, 6-4 win. Home fans were thrilled with the shock performance of the 28-year-old, who had failed in five previous matches at the elite level dating to 2003. All his attempts have come at home, the last at the Beijing Olympics, when he lost to Argentine David Nalbandian. The wild card is likely to see his luck run out in the second round, when he takes on fifth seed Jo-Wilfried Tsonga, winner of the weekend title in Tokyo over Mikhail Youzhny. With qualifying rounds concluding and a handful of first-round contests on offer at the event, which a year ago was played indoors in Madrid, German Andreas Beck earned a victory when Argentine opponent Jose Acasuso quit with knee pain trailing 7-6 (7/2), 1-0. Acasuso, who said he had been experiencing the problem over the last fortnight while playing in Asia, will be heading home to South America and then hoping to compete again in late October indoors in Vienna. I broke his serve 2-0 and then I felt pain all the time, said the number 51, who lost last week in the Beijing first round to Marat Safin. I cant run. Compatriot and US Open champion Juan Del Potro, the third seed behind Rafael Nadal and Novak Djokovic, continues his training after losing to a qualifier early this week as top seed in Tokyo. The shy South American, who stands fifth in the world, still appears stunned by his accomplishment a month ago when he took down Roger Federer in New York. Im still the same person, the same player, even though I won a Grand Slam. I do the same things every day. I know my way is to work hard, to be a better player, and of course I feel the matches. Im tired but I will try to win here. Del Potro said he was most looking forward to the brief off-season after Novembers World Tour Finals in London for the top eight men. When I finish the season, I need the vacation to be in good shape for next year. If I finish the season maybe four or three or even five or six, it would still be a good season.