From the Ann Arbor News:
In the second half, Sheridan took over at quarterback for Threet, who suffered an elbow injury before halftime.
Before people lose their minds over Michigan's loss to Toledo and call for people's heads because Sheridan was in the game instead of Threet, the official line is Threet got injured. Everyone please take a deep breath. Now come in off the ledge. It may get worse before it gets better, but it will get better.