Superstar hurdler Liu Xiang's stunning success at the Athens Olympics has turned out to be a double-edged sword, according to his coach, Sun Haiping. 'The gold medal has brought Liu a lot of fame, but at the same time he has also been roped into far too many commercial commitments. This has really impacted his performance on the track,' Sun said yesterday in Shanghai, where the 22-year-old Liu is preparing for tomorrow's Golden Grand Prix meeting. 'Liu has been spending far too much time endorsing products and not nearly enough in training. There is also a lot of pressure on him to compete in events around the world. So far this season, he has already competed at more than 20 meetings. That's too many, particularly if you are hoping to set fast times,' added Sun. Liu stunned the world when he won the gold medal at last year's Olympic Games in a world record-equalling time of 12.91 seconds. Since then, however, Liu's times have been more modest and he has been overtaken by veteran American Allen Johnson as the world's top-ranked hurdler. Sun, though, believes his charge will soon be back on top, starting with tomorrow's meeting where Liu will take on Johnson and highly rated Dominique Arnold of the US. There is added pressure on Liu as he will be competing in front of his hometown fans, who are expecting great things from their hero. But Liu appeared unfazed yesterday. 'I haven't really prepared much for this meeting but of course I am aware of the expectations and will definitely do my best,' he said. 'Johnson and Arnold are tough competitors, but if I perform to my best ability I will win.' His coach, however, is not so sure. 'I think Liu will be probably run 13.10 [in Shanghai]. 'Hopefully, the other competitors will be feeling the strain of a long season and will be slower than that,' said Sun. Johnson has hit form again after a disappointing Olympic Games in Athens, where he tripped during a heat and failed to make it to the final. He struck gold at last week's World Finals in Monaco and believes he has the momentum to win again in Shanghai. 'I hope I can repeat what I did in Monaco,' he said yesterday. 'But make no mistake, this is going to be a tough race, it's going to be very close. Liu and I are friends, but that's only when we are off the track.' Arnold, who has so often played second fiddle to Johnson, played down his chances of causing an upset. 'It's my first time in this part of the world.' 'It's certainly a difficult field. I'm just honoured to be mentioned in the same breath as Liu and Johnson,' he said. Tomorrow's meeting in Shanghai, the biggest of its kind in China, also features a number of other world champions, including 100m and 200m king Justin Gatlin, women's pole vault record holder Yelena Isinbayeva and Ethiopian distance runner Kenenisa Bekele, the Olympic 5,000m gold medallist. Organisers said yesterday that a full house of 41,000 was expected at the Shanghai Stadium.