Blackburn (forearm) threw off a mound for the first time in his rehab Sunday, Michael Wagaman of MLB.com reports.
Blackburn had worked up to throwing from 90 feet earlier in the week. The 24-year-old right-hander has been sidelined since late in spring training, but recent developments have manager Bob Melvin encouraged. "He is on the mound so there's a natural progression that we go through to get them ready to go pitch rehab games," Melvin said. "It's still a little bit of a progression but the fact that he's throwing off the mound is very encouraging."