Mariano Rivera is 42 years old, and this is the last year of his existing contract with the New York Yankees. Before the season started, there was speculation that he would retire in the fall. And then after Rivera tore his ACL Thursday night, there was speculation that we might've seen the last of him as a major-league pitcher. A torn ACL almost certainly means that Rivera's 2012 is over. He could've opted for retirement, rather than choosing to come back.

Mariano Rivera is choosing to come back. As he tweeted himself:

Thank you fans, friends and family for your prayers, well wishes and support. I will be ok.I will be back.

— Mariano Rivera (@MarianoRivera) May 4, 2012

And, as he re-tweeted:

"I'm coming back. Write it down in big letters. I'm not going out like this." - Mariano Rivera to reporters today.

— New York Yankees (@Yankees) May 4, 2012

Plenty of people have been talking about how it would be a shame for Rivera's career to end on his ACL's terms. It would seem that Rivera agrees. While Rivera's accomplished just about everything there is to accomplish in baseball, the one thing he hasn't yet accomplished is walking away how he wants to. He's committing himself to a lengthy rehab so he can try to do just that.

Great news for the Yankees organization. Great news for baseball.