Baez will begin the season on the disabled list with a left thumb contusion, Jesse Rogers of ESPN Chicago reports.
The Cubs were optimistic that Baez would be ready by Opening Day, but it appears as though he just ran out of time in the spring to work his way back. Manager Joe Maddon had previously indicated it was more of a short-term concern, so the 23-year-old figures to be ready to rejoin the roster shortly after the minimum 15 days.