Stevenson (undisclosed) left the field as his teammates prepared for final sprints during Tuesday's practice, Andrew Callahan of the Boston Herald reports.
Per Callahan, Stevenson was a full participant right up until the sprints and skipped a scheduled media availability afterward, but it's unclear what led to his early exit. If he's picked up an injury, it would open the door for TreVeyon Henderson to handle all the first-team reps in the backfield.