Stephenson (neck) will start a rehab assignment at Triple-A Louisville on Tuesday, C. Trent Rosecrans of The Athletic reports.
Stephenson has been on the shelf since May 31 due to a neck strain, but he's set to take a step forward in his rehab process. He'll likely only need a few minor-league appearances prior to being activated considering he's only been on the injured list for 10 days.