Polymarket traders sharply repriced the National Bank Open market for Learner Tien vs. Ben Shelton, with the implied winning probability of the Over outcome in the first-set O/U 8.5 sub-market dropping to 50% from 84% an hour earlier, according to Catcher Predict monitoring. The 34-percentage-point move indicates a rapid shift in market expectations, a pattern often seen in prediction markets when participants respond to fresh information or possible breaking developments tied to the event.