St. Louis Cardinals pitcher Carlos Martinez will begin the season on the injured list as the two-time All-Star tries to work his way back from shoulder weakness.

Martinez will not appear in exhibition games. He is to throw on flat ground for the next week before moving to a mound.

Carlos Martinez's condition has improved since he received a platelet-rich plasma injection two weeks ago, manager Mike Shildt said. Jeff Curry/USA TODAY Sports

St. Louis has not announced a timetable for Martinez's arm-strengthening program. The pitcher received a platelet-rich plasma injection two weeks ago, and manager Mike Shildt said treatment improved Martinez's condition.

A 27-year-old right-hander, Martinez was the Cardinals' Opening Day starter last year but did not pitch for St. Louis from May 8 until June 5 because of a strained right lat muscle, then was out between July 19 and 30 because of a strained right oblique and between July 30 and Aug. 21 because of a strained right shoulder.

When he returned, he pitched out of the bullpen and had five saves. He finished 8-6 with a 3.11 ERA in 18 starts and 15 relief appearances.