Dolphins coach Adam Gase was caught a bit off guard that Tannehill's injury got "progressively worse" last week, and Tannehill could miss more than just Sunday's game against the Bears.
"It was such an unusual situation," Gase said. "Last week, we started the week and he was sore, but it got worse as the week went on. That's why we found ourselves in a position that we weren't really thinking we were going to be in.
"Anytime he's been banged up or some kind of injury, he's always progressed positively. That's why we thought we would get the same thing. That didn't happen. That's why we waited until the last minute."
Before game time Sunday, Brock Osweiler was named the Dolphins' starter.
Gase said Tannehill is "day-to-day" and "nothing has changed" since Sunday morning, when he last worked out in an attempt to play versus Chicago. The plan is for him to rest for a couple of days and see whether he feels better on Wednesday or Thursday.
Gase believes the late fourth-quarter sack-fumble by Carlos Dunlap on Tannehill in Week 5 at Cincinnati led to his current injury. Tannehill practiced on Wednesday and Thursday before being limited on Friday as the injury worsened.
In the mean time, Osweiler will take first-team reps until Tannehill is ruled ready to play. Osweiler stepped up Sunday by throwing a career-high 380 yards in a 31-28 overtime win against the Bears.
Gase said he's "not sure" whether Tannehill faces a long-term injury, but the coach has complete confidence that the 30-year-old quarterback will play again in 2018. When asked about Tannehill's situation, Gase quickly interjected, "Yes, he will be the starter" again when he's healthy.
The Dolphins will host the Detroit Lions on Sunday, and figuring out which quarterback starts could go down to the wire again. Gase said there is no deadline to name a starting QB because Osweiler and Tannehill both know the offense and the Lions' defensive scheme, which is very similar to New England's.
Gase declined to detail the specifics of Tannehill's injury, saying, "I'll know more when I can see him throw again."
"There's unknown for us. He might wake up on Wednesday, feel great and go out and throw. Then it'll be how he feels on Thursday," Gase said. "I just want him to be healthy. I want him to be right. I don't want him to put himself in a situation where he goes to do something and it's not there. If he needs to throw a ball a certain way and he can't juice it up the way he thinks he can, and then you throw a ball that doesn't come out right. That was my biggest thing going into this game. Can you make the throws when you want to make them? That's where we had a lot of discussion. That was his concern, too, 'What if I can't throw it the way I want to?'"
Tannehill has a history of being a tough quarterback. The Miami Herald reported that Tannehill played a December 2015 game against Indianapolis despite urinating blood after the previous week's game against San Diego. The concern in this particular situation is that Tannehill has been just as puzzled by what's happening and hasn't progressed as well as the team would have hoped so far.
"It's going to be about how he feels," Gase said. "We can be told by doctors, trainers, 'This is what we think is going to happen.' But he's one of those guys that has been opposite of what you're being told. This was the first time we were being told one thing, like, this is kind of unusual that he's going the other way and him agreeing that he didn't feel right. Normally, he'll try to go opposite of what they tell him."