"We decided to inject that to clear it up completely," Showalter said of a low back injury that has been hampering Matusz this spring. "It might push him back a day or two with his outing, but we're hoping that manages it."
Matusz felt the injury during his first spring outing.
Catcher Matt Wieters, slowed by a sore elbow, threw off flat ground on Tuesday up to 90 feet. It was his second throwing session since feeling the soreness.