AUSTRALIAN teenager Mark Philippoussis, yet to lose a singles match at the Marlboro Championships, succumbed to a back injury yesterday which forced him to retire from his semi-final match against Italian Andrea Gaudenzi at Victoria Park. The 18-year-old, only one year after winning the Stars of Tomorrow event for juniors, was tipped as the next Marlboro champion after a brilliant two weeks which included victories over Sweden's Stefan Edberg and the Netherlands' Richard Krajicek. But he pinched a nerve in his back minutes before walking on to centre court yesterday and retired after losing the first two games to Gaudenzi, who meets Edberg in today's final. Philippoussis' injury overshadowed Edberg's comprehensive 6-2, 6-2 semi-final victory over Spain's Sergi Bruguera which the Swede rated as one of his best performances for years. Philippoussis, who was clearly in pain even two hours after retiring, was told by physios to rest for five days which means he will miss next week's prestigious US$2 million Essen event in Germany. 'I was sitting on a practice court two minutes before the match and when I went to get up, I got these back spasms,' said Philippoussis. 'It has been niggling me for a few days. 'It is still painful, worse than before. I thought about not going on court at all and after two games, I knew there was now way I could continue playing. 'I've already pulled out of the doubles in Essen. I was supposed to take a week off after Essen and then play Moscow. I'm very disappointed because I was playing well. This is only an exhibition while Essen is a big tournament and I was really looking forward to playing there.' The Essen tournament features the world's top 20 players and 32nd-ranked Philippoussis would have taken part as a wild card entry. World number 19 Gaudenzi, who defeated top seed Goran Ivanisevic to reach the last four, admitted that he did not think Philippoussis would even start the match. 'I noticed in the locker room before the match that he could not even put his socks and shoes on properly,' said Gaudenzi. 'I'm sorry for the crowd that we did not get to play but these things happen in professional tennis to all the players. 'I'm lucky to get into the final. I'll just try to do my best. Stefan can play unbelievable tennis when he is at his best.' To help appease spectators after Philippoussis' retirement, Gaudenzi later returned to court to assist tennis coach Peter Burwash conduct a coaching clinic. Edberg's victory was tinged with controversy when Bruguera later blamed his defeat on the tournament's official racquet stringer. 'It was the stringer and because of that I had no confidence,' said two-time French Open champion Bruguera. 'I kept telling them to string it higher and higher but it was loose. I don't know why I went there, all the other players get their racquets strung outside.' Edberg said that he would never consider using the tournament stringer. 'I use the shop over the road,' said Edberg, who would not let Bruguera's complaints detract from his 48-minute victory. 'I played as well as I did four or five years ago when I was playing my best tennis,' he said. Dutchman Paul Haarhuis and his compatriot Jacco Eltingh won the doubles title yesterday with a 6-4, 6-4 victory over Americans Richey Reneberg and Patrick McEnroe.