Plumbing new depths, the Waratahs lamely surrendered a 17-0 lead with a listless display in front of exasperated fans on Friday night.
The Kings are the competition's dead men walking, consigned to the scrapheap in 2018 as part of SANZAAR's Super Rugby restructuring after managing just three wins in the past season and a half.
But the lowly South Africans may well have sounded the death knell on the Waratahs' finals hopes after reversing a record 72-10 loss to NSW in the two sides' only previous meeting, in Port Elizabeth four years ago.
"It was a pretty embarrassing performance from us," Waratahs captain Michael Hooper said.
"There was a lot of talk, not much action ... It's going to be a tough weekend."
Hooper laid the blame squarely on the NSW forwards and admitted the Tahs were suffering a crisis of confidence.
"There are scrum errors, lineout errors and then there is just handling - where does it stop?" the skipper said.
"It is probably just us not being confident at the moment.
"So it is probably a mental thing coming in to the game at the moment and it is tough to put my finger on what it is right now."
Looking to cash in on the Brumbies' heavy loss to the Hurricanes earlier on Friday night in Napier, the Waratahs looked on track for a desperately needed bonus-point win after opening up a sizeable lead with three first-half tries.
But the Kings had other ideas, racking up 26 points to clinch a memorable first win on Australasian soil before the Waratahs grabbed an after-the-siren bonus point with a consolation try to Taqele Naiyaravoro.
Powerhouse winger Naiyaravoro had opened the scoring with the first try of the night after Israel Folau tapped back a clever cross-field kick from Bernard Foley.
When winger Rob Horne and fullback Cam Clark both followed up with 99-metre tries, Waratahs fans could not have imagined such a collapse.
The depressing defeat leaves the Waratahs languishing eight points adrift of the Brumbies on the Australian conference ladder.
Photo: PHOTOSPORT Waratahs coach Daryl Gibson.