Houck (elbow) began a throwing program Monday with 25 throws from 45 feet, Ian Browne of MLB.com reports.
It's the first time he's thrown a baseball since he underwent a UCL reconstruction and flexor tendon repair six months ago. Houck will continue a deliberate rehab process over the next several months and hopes to make a late-season return, but it's likely the Red Sox will hold him back until 2027.