New Zealand Sevens rugby star Victor Vito is in doubt for this weekend's World Cup in Dubai due to a calf muscle injury.

Coach Gordon Tietjens said a scan revealed a minor tear in Vito's calf after their first training session in Dubai, and he rated the Wellington powerhouse a 50-50 proposition.

Titejens spirits were lifted when Vito took part in training matches last night against Australia and the United States, and he would be given as much time as possible to prove his fitness.

He hopes Vito would also play a part later tonight when New Zealand face Japan and Uruguay in training matches to top off preparations for their tournament opener against Italy at 3:54am on Friday.

Wellington's Julian Savea joined the squad in Dubai as cover.