Nick Mangold left the game vs the Jaguars with an ankle injury. In the post game press conference, Rex Ryan provided this update:
First thing, I might as well get it out of the way because I know you’re going to ask me about Nick Mangold. Sprained ankle; x-rays are negative. We will get an MRI tomorrow to find out a little more about it, but that’s where we’re at.
Here is a thread in the JetNation forums about the injury and it will be updated as more information is made available.