A hamstring injury to Isi Tu'ivai has robbed Hong Kong of a vital cog in their campaign to qualify for the 2001 Rugby World Cup Sevens this weekend in Malaysia. Valley winger Tu'ivai pulled a hamstring while training on Monday night with the 10-strong Hong Kong squad bound for the Malaysian Sevens in Kuala Lumpur, which doubles up as an Asian zone World Cup qualifier. 'We waited until [last night] to see if Isi could make it. But although he turned up for training he could not take part,' said Hong Kong Rugby Football Union spokesman Bob Brown. Tu'ivai has been replaced by DeA's Chan Fuk-ping. 'Hong Kong will miss Isi. It is a big blow, but in Chan they have got an experienced player,' said Brown. Hong Kong are grouped with Taiwan, Thailand, Sri Lanka and the Arabian Gulf in the preliminary round, which starts on Friday. The other pool comprises Japan, Malaysia, Singapore, China and India. South Korea have automatically qualified for the 2001 RWC Sevens in Argentina next January. The International Rugby Board has allocated three qualifying berths to Asia.