BMC Racing's captain, third overall at the start of the day behind overall leader Chris Froome (Team Sky), abandoned with 70 kilometres to race on the 17th stage to Pra Loup because of the resulting fatigue.
He arrived to the team bus after the stage and under pouring rain, he climbed out of the team car with a towel over his head and stepped onto the bus without saying a word.
Van Garderen never emerged to explain what happened, but team officials came out before the bus rolled down the road towards their hotel in Sisteron.
"From the start of the stage, he didn't feel good. He was developing a headache, he couldn't push on the pedals and couldn't develop any power," Doctor Max Testa told press huddled under the awning to escape the late afternoon rain.
"He has been fighting a respiratory infection since stage 13. He could manage it for a few days, and we hoped the rest day [yesterday] would help, but today was very hard at the start. So the combination and the fatigue that built-up in the last days cost him the race.
Van Garderen twice finished fifth in the Tour and had hoped for podium spot in 2015. He lost time to Nairo Quintana (Movistar), but appeared to be on his way to a top-three in Paris this Sunday.
In quickly became apparent however that the 26-year-old was not able to hold the pace of the peloton on the first day of the Tour in the Alps, and was forced to climb off on the category two Col de la Colle-Saint-Michel.
"This morning, he was feeling pretty good, not 100%, but not worse than the days before," Testa continued.
"Honestly, no, I didn't see this coming. I was hoping that he was over the worst part."
Though deciding not to poke his head out of the bus to say good-bye today, van Garderen met with the press yesterday in Sisteron down the road from Team Sky's hotel. He gave no indication that he would suffer so much today.
"I talked to him afterwards, when he came here. Now he is clearly shocked because he had to give up the race," Testa said. "Now it is more a psychological thing, physically now he is OK."
Van Garderen was dropped once and then again later in the 17th stage. When he stopped, he embraced Sports Director Max Sciandri and sat down in the red and black team car.
"It's a lot for anybody to take on their shoulders," general manager, Jim Ochowicz said at the bus.
"He is disappointed. He would have liked to have finished the Tour. The team has worked hard for him for two weeks now. He has a lot of pressure on his shoulders right now.
"I know he is feeling the pain, but he is an athlete, a professional athlete. He understands you win and lose and he'll bounce back from this."
It is too early to say if van Garderen will bounce back and race the Vuelta a España in August. Next year, in addition to van Garderen, the team are rumoured to have the services of Richie Porte, who is set to leave Team Sky at the end of this season.
Tejay van Garderen's BMC Timemachine
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