Callahan was placed on waivers by the Lightning on Sunday.
Callahan spent the 2025-26 campaign in Boston's organization before he inked a one-year deal with their division rival. The former AHL Providence alternate captain was a solid contributor each of the last four seasons, and he's coming off a season where he set a career high of 14 assists across 56 regular-season outings in 2025-26. He'll likely factor into a top-four role with AHL Syracuse to open the upcoming season.