Turnbull (back) is scheduled to make one more rehab start before being activated from the 10-day injured list, Chris McCosky of The Detroit News reports.
Turnbull looked sharp in his last outing, allowing just one hit over 3.2 scoreless innings while fanning seven against Triple-A Louisville on Tuesday. He'll need to prove his health in one more rehab appearance before rejoining the big-league club, however.