The Dutchman, who won the opening stage from a reduced peloton before finishing second behind Bryan Coquard in Friday's bunch sprint, had always suggested the Storheia summit finish – 3.5km at 11.8 per cent – might be too hard for him, especially after a four-month absence from road racing.
To stand a chance of keeping Alexey Lutsenko and Warren Barguil – both within 10 seconds – at bay he'd have needed to be at the very height of his powers. As it was, he was suffering with a head cold and, despite a spirited resistance, finished in 23rd place.
"I was not completely broken, but I got a bit sick last night," Van der Poel said. "I felt pretty bad on the bike all day. I tried, but I immediately felt there was not much I could do about it.
"My nose was blocked and I had a headache. Above all I had a lot of problems with my head and felt a bit sick."
It wasn't immediately apparent that Van der Poel felt so bad. He was up towards the front of a bunch that thinned rapidly on the narrow road and double-digit gradients of the first kilometre of the climb.
He started to suffer when Astana piled on the pressure, but fought doggedly to claw his way back to a select group of six with just over a kilometre remaining. The road, however, only grew steeper, and he fell away once more, this time losing significant ground as Barguil, Lutsenko, and stage winner Odd Christian Eiking opened the taps.
"I told the team at the start of the day that I didn't feel very well, but we tried it anyway, because I was the only one up there on GC," Van der Poel explained.
"But I knew immediately that it wasn't going to be. I'm not saying that if I was completely fit I would have been able to go with the best guys right to the end, but when I saw my power numbers, I normally should have been able to be there for much longer."
Van der Poel's chances of winning the race outright have gone but he still has an opportunity to grab another stage win on the final day on Sunday. The finishing circuit in Narvik is sure to make for a selective race and if he stays in the front group, few would fancy their chances on the uphill sprint to the line.
That is, of course, if his health improves. At this rate, he might not even take to the start.
"I hope it will be a little better by tomorrow," Van der Poel said. "If I'll feel well enough to start tomorrow, I don't know yet."