Diaz (oblique) has been hitting, throwing and catching bullpen sessions during workouts this week and is close to heading out on a rehab assignment, MLB.com reports.
The Astros haven't offered up an official timeline for Diaz's return from the left oblique strain that sent him to the injured list May 5, but if he's cleared to join a minor-league affiliate within the next few days, he could have a realistic shot at rejoining the big club by the middle of June. Since Diaz was deactivated, Christian Vazquez has taken over as the Astros' No. 1 catcher, with Cesar Salazar serving as Vazquez's backup.