The Cardinals placed Gray (hamstring) on the 15-day injured list Tuesday, Jeff Jones of the Belleville News-Democrat reports.
St. Louis already confirmed Gray would begin the season on the injured list, and that transaction is now official. The right-hander is scheduled to pitch in a minor-league game Thursday as he continues to ramp up his throwing program, and he could be ready to join the Cardinals' rotation in the second week of April when first eligible.