The Dutchwoman, the major pre-race favourite for the overall title, reached the finish line atop the steep ramp in Épernay with shoulders swinging, weaving across the road as she fought to limit her losses.
The explanation turned out to be sickness. Cyclingnews saw a visibly upset Van Vleuten referencing stomach problems when talking with team staff back at the Movistar bus. She declined to speak to reporters there but later offered an explanation through her team.
"It started two hours after the first stage [on Sunday], I started to feel not good. I could not eat or drink, and I was super tired. I felt empty," she said.
"Yesterday I felt very bad but it was actually a victory to finish the stage like that. Today I had my first normal breakfast so I felt it would be fine, but you pay the price for being sick for 24 hours."
Eurosport's Iris Slappendel, who commentates from an in-race motorbike, reported that she had seen Van Vleuten stop for a "very necessary" nature break during the stage.
Still, Van Vleuten had been strong enough to make the key selection over the Côte de Mutigny with 15km to go on a punchy finale in the champagne hills. However, on the penultimate climb of the Mont Bernon with 5km to go she started to struggle, and was dropped from the lead group of a dozen riders.
The Giro Donne champion managed to claw her way back on but was distanced again as soon as the ramp to the finish line kicked up with 350 metres to go.
She crossed the line in 10th place, 20 seconds down on stage winner Cecilie Uttrup Ludwig (FDJ-Suez-Futuroscope), and also conceded 18 seconds to the race leader, Marianne Vos (Jumbo-Visma), as well as Ashleigh Moolman-Pasio (SD Worx), Silvia Persico (Valcar-Travel & Service), Elisa Longo Borghini (Trek-Segafredo), and Katarzyna Niewiadoma (Canyon-SRAM).
"I played some poker yesterday but today I couldn't really play poker anymore," Van Vleuten said.
"I was 1000 times better than yesterday. But I still felt not ok. I had problems to follow on the last climbs. But first climb I was still fine, so that's a sign I'm getting better."
Although she moved up to ninth overall, Van Vleuten is now 1:14 off Vos' lead, and just under a minute behind Longo Borghini and Niewiadoma, who stole 30 seconds in a late break on stage 2. Still, considering her issues, she knows it could have been a whole lot worse, and remains optimistic as the race heads for the gravel on Wednesday and then hillier terrain later in the week.
"I lost some time again but yesterday when I woke up I didn't think about finishing the race. Now I'm still in the race and getting better and better, so I'm happy so far," she said.
"I don't have control. I can only focus on what I have in my control and that's focusing on getting better."
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Patrick is an NCTJ-trained journalist, and former deputy editor of Cyclingnews, who has seven years’ experience covering professional cycling. He has a modern languages degree from Durham University and has been able to put it to some use in what is a multi-lingual sport, with a particular focus on French and Spanish-speaking riders. Away from cycling, Patrick spends most of his time playing or watching other forms of sport - football, tennis, trail running, darts, to name a few, but he draws the line at rugby.
- Kirsten FrattiniDeputy Editor