We have known since early March that Mariano Rivera was retiring at the conclusion of this season.
But there are now scenarios developing in which the remainder of the Core Four also could call it a career.

Both Derek Jeter and Andy Pettitte said they want to table discussions about the future until after the season particularly not to bring personal matters into the Yankees’ playoff quest.
I still expect Jeter to play in 2014 but I do have some hesitancy after several members of the team said they could see the shortstop walking away rather than messing with his legacy if he does not believe he can get vitality back in his legs. And after implying in spring training he had his sights set beyond just 2013 Pettitte now speaks of having to make a decision on whether he wants to “go through this grind again.”

When I asked Jeter directly whether he expects to be back he hedged several times before offering “I never imagine not playing. This has been my job for 20 years.”

Close but not a definitive “Yes I am going to play.” Which would have been his response any other time in those two decades.
The respect for Jeter notably his fanaticism to keep important issues private until he is ready to address them left most personnel around the club unwilling to speak about the shortstop for the record. But two people I believe know him well — or as well as you could know such a guarded person — said there are circumstances in which Jeter walks away from his $9.5 million player option for next season.

They said Jeter would not let money dictate his decision. He has made a quarter of a billion dollars on the field tons more off it and remains incredibly marketable. Instead the Jeter-Joe DiMaggio comparison was cited. DiMaggio retired when his production and body betrayed him because if he couldn’t be Joe DiMaggio he didn’t want to play. His dignity and legacy meant too much to him.