Cardinals starter Michael Wacha picked up a baseball Tuesday and did what he had not done in six weeks — threw it, with intentions. He remains as much as a month away from doing so in competition, but just playing catch was reassuring. “I don’t feel any pain in the shoulder or anything like that,” the young righty said after some light tosses. “It definitely feels strong. It feels alive, really.” Keeping it that way remains the Cardinals’ chief concern. Wacha gained clearance Monday to begin a throwing program after another MRI of his right shoulder showed continued healing of a stress reaction of his scapula. The condition, which involves a weakening of the bone and is a precursor to a stress fracture, is related to usage and can be a chronic injury. Yankees starter Brandon McCarthy, who has also dealt with stress reactions in his career, has had the injury happen in consecutive seasons. One of the reasons the Cardinals and their medical officials delayed Wacha’s return to a throwing program was to work on preventative measures before rehab started. Wacha, who has not pitched since mid-June, has been doing a workout program to build strength in his legs and torso, and also increase flexibility and strength around his right shoulder. The goal, the Cardinals have said, is to lessen the strain on the scapula and within the rotator cuff by building strength in other areas of his body.