MELBOURNE, Australia -- A new format called Fast4, which some have dubbed disco tennis, was previewed on Wednesday and Rafael Nadal, still recovering from appendix surgery two months ago, was only too happy to be on the dance floor.

The occasion was the official opening of the newly renovated Margaret Court Arena that will give the Australian Open, which starts on Monday, its third stadium with a retractable roof.

On Wednesday, 7,500 fans crammed the arena for a benefit night for the Rafa Nadal Foundation which assists socially disadvantaged youth.

It also showcased Australian-developed Fast4, which features four major rule variations to speed up the action for players and fans -- no advantage scoring, lets are played, and best-of-four sets.

Nadal's 4-1 first-set win against an Australian junior lasted 17 minutes.