It revived memories of his Shanghai Masters meltdown in October, where he clearly tanked a series of points and was later handed a three-week ban from the ATP tour.
The 21-year-old made sure points didn't last long in his Hopman Cup clash with Sock.
Second-serve ace attempts were a common sight and Kyrgios also committed a glut of unforced errors, while trying to land audacious winners.
Kyrgios carried the knee injury into the Hopman Cup, but maintained it was so minor that it didn't even warrant scans.
However, Kyrgios finally underwent an MRI yesterday morning, with the scan showing up the "start of some bone stuff in my knee".
"It's not terrible, but it's not great," Kyrgios said. "I just need to rest now, and a couple of days without the load and I should be back to normal.
"I think I have some time. A thing like this won't take too long."
Kyrgios is scheduled to play two more events before the Australian Open (January 16-29).
He was set to partner Bernard Tomic in Monday's Fast4 doubles clash in Sydney, before fronting up for the January 10-12 World Tennis Challenge in Adelaide.
Kyrgios isn't sure whether he'll be able to fulfil those commitments, but he remains optimistic about his chances of playing well at the Australian Open, despite his injury.
"I'm not the type of guys who needs plenty of matches before a Grand Slam," Kyrgios said. "I played two really good games here and obviously the knee was getting worse every day.
"I've got four days now to go home, see my physio, ice it and rest it, and that is ample time for it to settle down."
