Garrard signed in March and climbed atop the depth chart in training camp before he was sidelined by a left knee injury that required arthroscopic surgery Aug. 11. In his absence, Tannehill claimed the starting job for Sunday's opener at Houston.
The Dolphins also placed guard Artis Hicks on the reserve-injured list Tuesday, and they re-signed tackle Ray Feinga, who was waived by the team Friday.
The 34-year-old Garrard's $2.25 million salary would have been guaranteed if he was on the roster for the opener. He returned to practice Monday on a limited basis and said he's not yet 100 percent.