Turnbull will run into an innings limit at some point in the second half, Evan Woodbery of MLive.com reports.
Manager Ron Gardenhire didn't give a specific innings total or date at which Turnbull would be shut down, but it makes sense for the Tigers to be cautious with their young arms in a season in which they aren't close to the playoff race. Turnbull threw 135.2 innings last year and is at 98.2 so far this season.