Boxberger (back) threw 15 fastballs in his first bullpen session Tuesday and emerged setback-free, Marc Topkin of the Tampa Bay Times reports.
It was a modest but important step for the right-hander, as it marked his first time throwing off a mound since suffering his injury in spring training. Boxberger will presumably take at least a day off before attempting another session, with the likelihood that he'll push his pitch count and intensity up a notch or two.