Young Australian tennis star Nich Kyrgios has been forced to withdraw from the Hopman Cup because of a back injury.

The teenager, who knocked out Rafael Nadal at Wimbledon, will be replaced by Matthew Ebden.

• Philippoussis urges Kyrgios to ‘train smart’

Hopman Cup organisers tweeted late on New Year’s Eve: “Nick #Kyrgios has been forced to withdraw from #HopmanCup due to a back injury. We welcome WA’s own @MattEbden to replace him.”

Kyrgios tweeted: “I’m gutted to miss the Hopman Cup.”

Injury-free for the first time since charging into the Wimbledon quarter-finals in July, Kyrgios was to have launched his 2015 campaign at the Hopman Cup in Perth from January 4.

Following the Hopman Cup, the 19-year-old Newcombe Medallist planned to contest the Sydney International before joining the world’s best at the Australian Open in Melbourne from January 19.