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Tannehill injured his knee on Thursday in training camp. He was running for the sidelines during a scrimmage when he planted his foot awkwardly and, without contact, fell to the ground.
Tannehill also injured his left knee in December of 2016 and missed the rest of the season.
The Dolphins and Tannehill are reportedly seeking second and third opinions, and no decision has been made. There is a possibility that Tannehill could miss 6-8 weeks, then try to return without getting surgery. According to NFL Network's Ian Rapoport, an MRI showed no structural damage to Tannehill's knee.
According to ESPN, there's some debate how Tannehill and the Dolphins handled the first knee injury. Tannehill opted not to get surgery, which one source told ESPN left his knee a "ticking time bomb." Now, with a second injury in less than one year, Tannehill may have to get surgery.
While the Dolphins have Matt Moore as a backup, and he performed capably when Tannehill went down last year, two other big names have been floated for spots with Miami: Colin Kaepernick and Jay Cutler.
According to ESPN's Josina Anderson, Kaepernick's name has come up with the Dolphins. Owner Stephen Ross was reportedly open-minded to Kaepernick's national-anthem protest last year and didn't mind when several Dolphins players also kneeled during the anthem.
Jay Cutler is also reportedly in the mix as he played under Dolphins coach Adam Gase with the Chicago Bears in 2015. Cutler is slated to enter the broadcasting booth for Fox this season, but would reportedly consider delaying the move if he could start and be paid starter's money for the Dolphins.