The 70-year-old Carew wears a battery pack and says he hopes to have a new heart in four months.
Manager Paul Molitor said it won’t be the last time people will see the T-shirts.
"We’ll keep these around," he said. "I won’t be surprised if we see them under the uniforms of our players."
During the workout, Carew spent time in the batting cages, talking to some of the players before he walked onto the field at Hammond Stadium. When he got there, he was greeted by recently retired outfielder Torii Hunter, and the pair hung out behind the cage.
"Rod means a lot to this organization," Hunter said. "For me, as a young kid, I had a chance to hang out with Rod. He helped me out in so many different ways. I really appreciate him and love him, have the utmost respect. When this happens to someone you love, it’s devastating."
Before the workouts began, Carew couldn’t help joke he might try to teach some of the young players how to drag bunt, turning into his left-handed hitter’s stance and taking a few steps, looking like he was heading out of a batter’s box.
"No drag bunts," he said after the workouts ended. "Not yet anyway."