Tannehill's agency, SportsTrust Advisors, announced the move on Twitter.
The Dolphins faced an uphill battle to flip Ryan for assets, given his bloated cap figure, so getting anything in return for him is a win for Miami.
The Dolphins will receive a fourth round pick in 2020 and a seventh rounder in 2019 while the Titans will also acquire a 2019 sixth rounder along with Tannehill. He had a wildly uneven season a year ago that ended badly.More news: Browns RB Kareem Hunt suspended for 8 games
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The new regime in Miami decided a fresh start was necessary headed into the 2019 season.
The Fins have virtually no backup QB. Miami's current depth chart is Jake Rudock and Luke Falk. You could argue that he and Tannehill are incredibly similar - both are athletic, accurate quarterbacks and their playing style feels similar. Tua will not be available next year. The Dolphins haven't really been linked to many quarterbacks in the upcoming 2019 NFL Draft, but that's largely a result of where they're picking.
Another possibility is Kyler Murray, the Heisman Trophy victor from Oklahoma, who worked out with the Dolphins yesterday.