Rafael Nadal tries his hand at some disco tennis

MELBOURNE, Australia (AP) A new format called Fast4, which some have dubbed disco tennis, was again on display Wednesday with a recovering Rafael Nadal 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 into the arena for a benefit night for the Rafa Nadal Foundation, which assists socially disadvantaged youth.

It also showcased the Australian-developed Fast4, which features major rule variations to speed up the action for players and fans - no advantage scoring, lets are played, and the first to win four games wins the set.

The often no-nonsense Nadal, introduced to the crowd through a haze of dry-ice smoke and loud music, clearly enjoyed the new format. He joked with the spectators on numerous occasions and once playfully hit a ball into the crowd when someone interrupted him during a serve. He also took ''selfies'' with his mobile phone.

Earlier, Nadal trained at Melbourne Park, indicating he might be overcoming health and injury issues.

Nadal was sidelined for three months with a right wrist injury after Wimbledon. He briefly returned in Beijing in late September, advancing to the quarterfinals. He then had appendix surgery in early November, which he is still recovering from, saying last week in Qatar that he was far from 100 percent.

''This is the third comeback of my career after injury, so we will see how it goes,'' Nadal said.

On Wednesday night, playing Fast4, he beat former Australian player Mark Philippoussis in 15 minutes, and won 3-2 against Fernando Verdasco, who earlier in the day beat Gilles Simon in straight sets across town at the Kooyong exhibition tournament.

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