Yankees Core Four

After 2010, Pettitte retires.
After 2011, Posada retires.
After 2012, Rivera retires.
After 2013, Jeter retires.

All four retiring, one at a time over four years, drip-drip-drip-drip?

The first two have happened.

The third has been hinted at by the player himself.

The fourth is less likely than the third. Jeter's contract runs out after 2013 but there is a player option for 2014. So he may hang on one more year, unless his performance reaches the point where he feels that to play would be detrimental to the team. Which is conceivable.

It would be quite the way for the "Core Four" to exit.