The 28-year-old fought his way through an attack-filled finale and found himself in a small group with team leader Thibaut Pinot, race leader Michal Kwiatkowski (Team Sky) and six others - all looking at each other and coasting down the hill with less than a kilometre to go.
With nothing to lose, Preidler mashed on the pedals, dove right and flew away down the descent - tucked low on his top tube - then hurtled through the technical last few hundred metres to hold off Bora-Hansgrohe's Emmanuel Buchmann to take the victory.
"It's very important," Preidler said of his first WorldTour win. "I'm really happy. I've been looking for a long time for a victory like this. It's almost my seventh year as a professional. So finally I could win in the WorldTour. I've been close but never on the top step."
The 129km stage from Zakopane to the Bukowina resort was littered with climbs. An early breakaway focussed on the mountains classification stayed away until the penultimate climb when BMC's Rohan Dennis attacked. Next, Sunweb's Sam Oomen and Dries Devenyns (Quick-Step Floors) got away, and when they came back, LottoNl-Jumbo's George Bennett took a turn. But Sky successfully chased back each threatening move for Kwiatkowski.
"It was a hard and fast day and really stressful," Preidler said. "Sky was in control of everything and no team had actually a chance. For me, I just saw a chance to try something on the last 500m because the final was quite technical. I just jumped away at the right moment."
A three-time national time trial champion, Preidler said he had some confidence he could pull off the win.
"I know my qualities and know I can do one kilometre quite fast."
Thanks to the move, Preidler climbed into the top 10 overall, just 29 seconds behind the race leader, and one second behind teammate Pinot. There's another 139km stage in the same region as Thursday's finish - and six first category climbs on the route. When asked if Groupama-FDJ could tag-team and unseat Kwiatkowski, Preidler was not sure.
"I have no idea but Sky looks quite strong. Of course, first we will have a meeting tomorrow and then we will make the tactic."