The Panthers signed Sullivan (abdomen) to a reserve/future contract Wednesday, Will Bryan of the team's official site reports.
As a rookie with Seattle this past season, Sullivan only appeared in one game a Week 8 contest against the 49ers in which he played one snap on special teams. The 2020 seventh-round pick should at least now be fully recovered from his November sports hernia surgery, but he'll be looking to impress with a new organization heading into the 2021 campaign.