The worst of Nick Kyrgios was on display on Thursday night in a 6-2 6-2 Hopman Cup loss to American Jack Sock at Perth Arena.

Kyrgios lacked energy in the dead rubber tie, blasting a series of unforced errors in a match that lasted just 49 minutes.

Two days earlier, the 21-year-old promised to have some fun against his good friend Sock.

But Kyrgios rarely cracked a smile during the one-sided contest.

At one point, he decided to volley a Sock mis-hit that would have otherwise sailed out by about five metres.

Kyrgios’ shot crashed into the net.

Australia’s Hopman Cup title hopes were already over after suffering shock 2-1 losses to both Spain and the Czech Republic earlier in the tournament.

Kyrgios had performed well in both of those ties, winning his singles matches.

But against Sock, he was clearly off the boil.

Kyrgios hit the headlines for all the wrong reasons in October when he was banned from the ATP tour and ordered to undergo counselling after tanking several points during a shock loss at the Shanghai Masters.

Daria Gavrilova will take on world No.36 Coco Vandeweghe in the women’s singles rubber.