Two-time champion Jurgen Melzer suffered his earliest defeat in five years at the Austrian Open on Wednesday as the fourth seed went out in the second round, losing to Gilles Muller, 6-3, 3-6, 7-6 (7/4). The result at the Stadthalle was a huge disappointment for the newly-married 31-year-old, his ranking down to 37 after a number of injuries including a hip problem. Melzer admitted at the start of the week that he was going into the European indoor season with a loss of form, but remained encouraged by his recent Beijing quarter-final run. But the Austrian was unable to cope with 18 aces from Muller, a Luxembourg journeyman about to turn 30 without a career title. \"I had trouble with my first serves and he was serving very well. He had some real bombs,\" said Melzer. \"It was not my day out there. I\'m sorry to lose so early, especially at home where I\'ve had success.\" Melzer, who recently married fellow pro Iveta Benesova, hung tough in the final set to force a tiebreak. He recovered from 0-3 down in the decider but could do little as Muller unleashed a pair of big serves to wind up the evening, finishing the job with a return winner to the open court. Dieter Thiem, 19, who ended the career of comeback king Thomas Muster a year ago at the same venue, defeated Slovak Lukas Lacko 7-6 (7/3), 6-3 to keep home hopes alive. Top seed Juan Martin del Potro was making his indoor start after a month away with a wrist injury, facing qualifier Daniel Brands later Wednesday. The world number 111 German made a surprise appearance in the Vienna semi-finals a year ago. The outsider also stands 2-3 against top 10 players, beating Gilles Simon in 2009 and Nikolay Davydenko in 2010. Del Potro is struggling to claim one of three -- possibly four with the injury absence of Rafael Nadal -- places in the year-ending ATP World Tour Finals in London next month. He currently stands provisional seventh in the qualifying field for the eight-man event in which Roger Federer, Novak Djokovic, Andy Murray, Nadal and David Ferrer have already booked their places.