Porte kept his powder dry until the final climb of Willunga up to the finish - the second ascent of the hill on the 151.5km stage that had started three-and-three-quarter hours in McLaren Vale.
But while at this point of the race in 2017, Porte was already in the ochre leader's jersey, and had all but sewn up victory before the stage had started, this year the Tasmanian went into the stage lying 20th overall, 14 seconds behind race leader Peter Sagan (Bora-Hansgrohe).
"It was such a hard lead-in there at the bottom when Cannondale [Education First-Drapac] put it in the gutter. I felt great, and the guys looked after me all day, but it hurt so much," Porte admitted.
And while Sagan's efforts to hold on to the race lead fell apart on Willunga, his Bora teammate Jay McCarthy tried valiantly, but in vain, to keep pace with Porte in the final couple of kilometres of the stage.
"I couldn't look back - I just had to go," Porte said. "But of course you look back a bit, and I could see that Jay was strong to start with, but I think this stage is much better for me than it is for him. I must admit, though, that with 300 metres to go I did think that maybe I'd gone a little too hard."
In those final few hundred metres, it was South Africa's Daryl Impey (Mitchelton-Scott) who emerged from the melee to snatch the race lead, albeit on the same time overall as Porte.
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"Daryl is quick: he's been second two times here this year on stages to guys like Sagan, so realistically I don't really have a chance to move up [and win overall], because if I start going, guys like [Impey's team-mate] Caleb Ewan are just going to go for the intermediate sprints," Porte said.
Was he really conceding the overall TDU win to Impey, despite the bonus seconds available on Sunday's final stage in Adelaide, both at the intermediate sprints and at the finish?
"If I was good enough to win, I would have won it today on Willunga, so hats off to Daryl: he's a good mate and a fantastic bike rider. I have to be happy with second, to be honest.
"I'm happy with where I am, all things considered. I mean, I had a tough last half of last year," he continued, referring to having crashed out of the Tour de France, "so to be up here and to win at Willunga for a fifth time, I have to say I'm happy. But of course I would have loved to have won the overall."
Now, Porte's attention turns to the rest of his season, and to continuing to improve, having ticked off his first race back following that Tour crash.
"I've had a fantastic bunch of people around me, from my team to my wife and family. It has been a tough time, and it was a nasty crash that knocked me around, but I think I can maybe have the best season of my career, and I'm motivated for that."
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