Nadal to headline Sydney exhibition

World number five Rafael Nadal will headline the Fast4 exhibition event in Sydney in January, Tennis Australia said on Thursday.

The Spaniard joins Frenchman Gael Monfils and local favourites Lleyton Hewitt and Nick Kyrgios in the short-form format.

Next year's event has been expanded after the inaugural one in 2015 only featured Roger Federer and Hewitt. An experimental format is used in the event, with sets won by the first player to four games, play continuing following let calls on serve and no deuces.

The format has been billed as the tennis equivalent of T20 cricket and has proved to be something of a commercial hit in Australia.

"It's easy for the crowd to get involved in every point which makes for a great atmosphere," 14-time grand slam champion Nadal said after receiving an invitation.

Nadal and Monfils will be partnered seven-time grand slam winner John McEroe in a world team, while Hewitt and Kyrgios will team up with former Wimbledon champion Pat Cash in an Australian team.

The tournament takes place the week before the Australian Open starts on January 18 in Melbourne.