He was the leading candidate to start at center this season.
But last week in an OTA practice, Teague went down with what is being described by a league source as "serious ankle injury."
Teague hasn't been present at the minicamp, and Mangold has been starting.
One of the hardest position in the NFL for a rookie to start, is at center. Not only do you have to handle your own assignments, but you are the leader of the offensive line. A big part of the job is making line calls after seeing how the defense lines up. For a rookie, this is very hard, because they haven't seen a lot different NFL sets while on the college level.
This is why the Jets were considering starting Mangold at guard as a rookie, and going with the veteran Teague at center.
But that plan now has to be altered due to Teague's injury.