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  Del Potro secured a 3-6 6-3 7-6 (7-2) 6-3 victory over the Swiss player.
  The Argentine is 165th in the rankings after missing more than two years because of injury problems.
  Del Potro, who is in the same half of the draw as Britain's Andy Murray, will next play either France's 32nd seed Lucas Pouille or American Donald Young.
  I am pulling for Del Potro and every player in the locker room is. No player deserves what he has had in the last three or four years.
  Former US Open champion Del Potro, 27, reached the Wimbledon semi-finals in 2013 but the former world number four is playing in his first Grand Slam since the Australian Open in 2014 after having three wrist operations.
  He struggled early on as Wawrinka, 31, claimed an early break before comfortably taking the opening set, but Del Potro fought back well to take the second.
  Both players broke serve twice in the opening four games of a thrilling third set, which Del Potro won in a tie-break, before taking the fourth set to wrap up victory.
  "It feels amazing," Del Potro told BBC Sport. "I beat one of the guys who is playing great tennis this season and I couldn't have expected this before today.
  "I enjoyed the crowd, they were incredible and I'm very happy.
  "It is my second or third career now after all the injuries. I was sad for the last two years and now I am enjoying playing tennis again. I feel alive."
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  Australia's Nick Kyrgios is also in the same half of the draw as Murray and remains on course to meet the world number two in the last 16.
  The number 15 seed came from two sets to one down to beat Germany's Dustin Brown 6-7 (3-7) 6-1 2-6 6-4 6-4 in a thrilling, rain-affected second-round match on Court Two.
  The pair had only played three points before a rain delay of more than three hours with the German, ranked 85th in the world, then clinching the first set on a tie-break.
  Kyrgios swept through the second set in just 15 minutes but Brown regained the advantage by taking the third.
  However, the Australian then won the fourth to move level and, after another rain delay, clinched the fifth set to reach round three.
  Spanish 22nd seed Feliciano Lopez will play Kyrgios in the third round, with the winner of that tie then playing either Murray or Australian John Millman in the last 16.
  Lopez fought back from two sets behind to defeat Italian Fabio Fognini 3-6 6-7 6-3 6-3 6-3.
  Elsewhere, there were routine victories for 10th seed Tomas Berdych and 12th seed Jo-Wilfried Tsonga.
  Berdych beat Germany's Benjamin Becker 6-4 6-1 6-2, while Tsonga triumphed 6-1 6-4 6-3 over Juan Monaco of Argentina.
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target: Juan Martin del Potro has recorded a shock second-round win to knock fourth seed Stan Wawrinka out of the men's singles at Wimbledon.