Porte has won atop Willunga the past four years with the same trademark move - an attack approximately 2km from the finish - that no-one in that time has been able to closely answer.
The 32-year-old will enter the 151.5km fifth stage sitting 20th overall - 14 seconds adrift of tour leader Peter Sagan, who was short on words when asked how his BORA-hansgrohe team could respond to and thwart the defending race champion.
"We will see, altogether," the Slovak offered after his own triumph in Uraidla.
Sagan insists he is in Australia "just getting condition", and the outfit will race, as planned from the outset, for Jay McCarthy, who is third overall behind Daryl Impey (Mitchelton-Scott).
Porte complained of feeling ill overnight but looked comfortable in stage four yesterday despite a second consecutive day of temperatures in excess of 40℃. The Tasmanian finished in the front group of 35 riders along with BMC teammate, Rohan Dennis.
"Hopefully tomorrow we can recover and Rohan and I can have another good day," he said. "It's not a terribly hard climb. Sagan is in such good form, so he's also a danger."
Climber George Bennett (LottoNL-Jumbo), eighth overall, exchanged pleasantries with Porte in the final yesterday and was later divided on the Willunga contest he himself could still profit from.
"I can't get rid of him [Porte], probably can't get rid of him in a sprint, there's no easy way around it," Bennett said. "Stick on his wheel? I don't know.
"I think Sagan could win tomorrow because it's a headwind and it's hard to go alone.
"Tomorrow decides the race. Sagan will be hard to beat but so is Richie. Richie on the Hill is in a league of his own. He wasn't even breathing today so I think tomorrow we will see him come out."