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As the Dolphins prepare to face the Jets on a special edition of Thursday Night Football, Miami’s starting quarterback is recovering from a significant knee injury suffered six days ago against the Cardinals.

Per multiple sources, Tannehill’s left leg currently is in a cast. The cast has been added to assist with the healing of the MCL, a rope-like ligament that will repair itself over time, unless it’s fully torn.

As one source explained it, Tannehill has a Grade II MCL sprain, which entails significant tearing of the ligament, along with considerable pain and tenderness. In many cases, a Grade II MCL tear requires a 4-6 week recovery period.

The best news the Dolphins received in the aftermath of Tannehill’s injury is that the ACL in his left knee isn’t fully torn. There is, however, a slight tear of the ACL.

Tannehill nevertheless could play as early as Week 17, against the Patriots. He also could be placed on injured reserve and shut down for the year. For now, the team doesn’t know how the situation specifically will proceed — and the team won’t know until Tannehill is able to begin moving around on the leg.

There’s also a chance Tannehill will need reconstructive ACL surgery, since the slight tear in his ACL won’t heal on its own. As one source noted, it’s likely that many players in the NFL currently are performing with slight ACL tears that have no dramatically diminished the stability of the joint. With further injury, however, surgery can become necessary.

Ultimately, the Dolphins will be smart with Tannehill’s injury. He has shown this year that he can be the quarterback they envisioned when drafting him in 2012. Even if he can’t play again in 2016, they want to be sure he’ll be ready to go in 2017.