So why has he remained on the roster?
"There's just some contractual issues we're trying to work out," Lions general manager Bob Quinn told reporters at the league's spring meetings in Boca Raton, Florida. "I really don't have anything to add. As of today, Stephen is still on the roster."
Quinn would not go into specifics why Tulloch has not been released but did tell reporters the team had to pay his $500,000 bonus because it was due.
Tulloch was Detroit's leading tackler last season but announced on Instagram in February he wouldn't be returning to the Lions in 2016 and thanked the fans for his time with the franchise.
The new league year passed and Tulloch was still on the roster at that point. A source told ESPN earlier this month the plan was still for Tulloch to be released.
That just hasn't happened yet.
Tulloch became a part-time player for Detroit during the 2015 season, often coming off the field in passing situations.
The Lions re-signed Tahir Whitehead during the first few days of free agency and he and Josh Bynes should compete for the middle linebacker spot. It's also possible Detroit drafts someone to compete with both of those players in the middle.