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I don't believe the wrist had some impact because he started soon on the turbo trainer, and he was producing his best performances ever in the Tour.
He just had a bad day, he didn’t fade during the rest all of the third week. He did a great ITT and won stage 20 in the vosges.
If i remember correctly, he had a crash on la loze stage, and also he had gastric problems, that seriously affected him. I think this were the main factors who prevent him from doing a expected performance on La Loze stage.
Nevertheless, in normal conditions, i believe Pogacar would not take time on that stage, i believe he would lose 45 s/1 min on col de la Loze to Vingegaard. It was a stage with >5000 m vertical meters, altitude, more suited for Vingegaard.