German veteran Tommy Haas continued his comeback after hip surgery with an upset of fifth seed Juan Ignacio Chela in a 6-7 (3/7), 6-3, 7-6 (7/5) victory to reach the second round of the Austrian Open here on Tuesday. Haas, who won this event a decade ago, needed four match points to get past Chela in what is only his second top tier event in two years. Austrian favourite and former world number one Thomas Muster, 44, was set to play as a wild card later, taking on 18-year-old fellow compatriot Dominic Thiem in a showcase match between locals. Muster has won just two of 23 matches on the Challenger circuit since making a comeback 14 months ago. The 1995 French Open winner has said that this week will be his swansong at this level - while not ruling out continuing at the Challenger events. Italian eighth seed Fabio Fognini advanced as Spain's Tommy Robredo quit injured, 7-6 (9/7), 5-7, 2-1. Slovenian Ajaz Bedene got through when Ivo Karlovic retired after the first set with back pain, handing over a 7-6 (7/0) win. German Daniel Brands beat Austrian Martin Fischer 6-7 (3/7), 6-2, 7-6 (8/6) while another German Philipp Petzschner put out Spain's Pablo Andujar 6-2, 6-2.