So far, there hasn't been much action on the open market involving linebackers. There are plenty of talented guys out there, but things have been slow to develop, which is part of the reason why we haven't heard much news about Stephen Tulloch visiting other teams. Another reason for that may be related to his contract demands. From Anwar Richardson:

According to sources, Tulloch is seeking a long-term deal worth more than Cleveland's D'Qwell Jackson's five-year deal, which is worth $42.5 million ($19 million in guarantees and bonuses). He is seeking a contract that will pay no less than $6 million a year, with no less than 40 percent of his deal guaranteed. It is unclear how much Tulloch wants in bonuses and incentives.

Thanks to Calvin Johnson's new deal, the Detroit Lions now actually have the cap space to work out a deal with Tulloch. That doesn't mean they will overpay him, though. That's not to say that the Lions think at least $6 million a year for Tulloch would be overpaying him, but it would be a big raise over the $3.2 million he made last season.