Allen suffered a sprained UCL in his left thumb during a dive into first base Saturday while playing at High-A Dayton, C. Trent Rosecrans of The Athletic reports.
Allen was sidelined with an elbow injury during spring training and is now expected to miss the next several weeks due to the thumb injury. The outfielder went 1-for-9 with five strikeouts through his first three games with Dayton.