Winn was scratched from the lineup for Tuesday's game against the Diamondbacks due to left thumb soreness, Derrick Goold of the St. Louis Post-Dispatch reports.
It's unclear when exactly Winn sustained the injury, as he's in the midst of a seven-game hit streak during which he has gone 11-for-28 (.393 average) with two doubles and a homer. The 24-year-old should be considered day-to-day as he continues to be evaluated.