Successful college football teams aren't built on transfers, but they can provide a key boost to a new team.

Whether it's adding a new signal-caller, upgrading at receiver or fortifying either side of the line of scrimmage, transfers can address a weakness or help replace a departing standout.

The highest-profile players have already picked their new home, but a handful of impact transfers are still available.

While undergraduates were considered, the best remaining options are all graduate transfers who will be eligible immediately. One of themu2015the top quarterbacku2015even has two seasons left to play.

Zach Abercrumbia, DT

Jim Harbaugh picked up an impact grad transfer in Central Michigan end Mike Danna, but was he all Michigan could wind up taking?