Cashman said, via the ESPN New York report, "He wasn't certain on what he is going to do."
Rivera, who will turn 43 years old on Nov. 29, tore his ACL in early May while shagging fly balls before a game against the Kansas City Royals.
After the injury, Rivera said, "I'm coming back. Put it down. Write it down in big letters. I ain't going down like this."
But that may have been more reactionary than logical.
After all, Rivera is in his 40s now and coming off a torn ACL. On top of that, he has nothing left to prove.
He's won five championships, been selected to 12 All-Star Games, was named the World Series MVP in 1999 and has the most career saves (608) in MLB history.
The ideal scenario for Rivera is coming back next season and winning a World Series before he retires, but there is no guarantee that will happen (especially after what happened to the Yankees this season), and he only risks further injury.
Rivera is a warrior—he wouldn't have accomplished what he has throughout his career if he wasn't.
I understand pure passion is all that is driving him at this point, and I understand that it's hard to walk away from a game you've given your heart and soul to for the past 18 seasons.
But at some point, Rivera has to realize that perhaps it's his time to go, and maybe that's where his words are coming from now.
It's one thing to want to do something; it's quite another to physically do it at his age.
If it really does come down to Rivera hanging up his cleats, it will be a sad moment for baseball.
Rivera embodies everything you want in a player and he's a surefire first-ballot Hall of Famer.
One thing is for sure—hitters won't miss the greatest closer of all time.