Rivera said that he decided what he wanted to do within the last two or three weeks, and that he has already let his family in on the secret. The Yankees, Rivera said, will be the next to know.
"That will be my decision," Rivera said. "Even if I save 90 games, even if they want to pay as much money as they want to -- anything."
Promising that he will announce his intentions publicly during the season, Rivera acknowledged that coming to a final decision had been difficult for him.
"Definitely, decisions like that are always hard, always," Rivera said. "It involves what you do, it involves what you have done for 22 years, you know? Decisions like that are always hard, but at the same time, they have to be made."
The owner of a Major League-record 603 saves, Rivera went 1-2 with a 1.91 ERA in 64 appearances last season, and is entering the final year of a two-year, $30 million contract.
Rivera has hinted at retirement previously only to sign new contracts, a fact the right-hander acknowledged. But he said that this time his decision is "irrevocable."
"How many times have I told you guys that this is my last year?" Rivera said. "Seven, eight years? I keep telling guys, after this year, I'm not going to play [any] more. Then there it is, I play two more years, a contract for three more years. Then another three more years.
"But this one is different. This is it. This one is my decision. When I let you guys know what it is, you guys will know."
At Jorge Posada's retirement news conference on Jan. 24, Posada said that Rivera told him 2012 would be his final season. Posada quickly clarified that he didn't believe Rivera will actually follow through.
"Mariano said this is it," Posada said that day. "He said he has one more year, but Derek [Jeter] said he's got like three more to go. ... I don't think [he'll retire], especially the way [Rivera] keeps playing."
On Monday, Yankees manager Joe Girardi said that he hadn't discussed the future with Rivera.
"He hasn't really talked about how much longer he wants to go," Girardi said. "That's a decision that's inside his heart, and he's probably a guy that will make it after the end of this year. But he has not told me anything."
Girardi said that the Yankees have been fortunate to receive so many years of service from Rivera, who debuted with the club in 1995 as a starting pitcher and harnessed pinpoint command of a devastating cutter for a march to the top of the saves leaderboard.
"I would say if he was 32 and we asked everyone in this room, 'Do you think he'll still be pitching at 42?', I don't think a lot of us probably would have said yes," Girardi said. "So it's a blessing, and the Yankees have been blessed well."
Rivera has said that it is becoming more difficult to leave his family for Spring Training. Last year, he noted how it tugged at his heart when his youngest son, Jaziel, cried and clutched his leg as Rivera tried to leave their suburban New York home.
"It's all separation. That's it," Rivera said on Monday. "It's just separation from the family."
He said that he still enjoys seeing friends and familiar faces once he gets to Tampa, and that he still savors the grind of workouts -- even seemingly mundane tasks like fielding practice, as Rivera did with teammates half his age on a back field Monday.
Perhaps Rivera is taking the time to soak in those moments even more now. Following his workout, after most of his teammates had retired to the clubhouse for showers or weight-lifting, Rivera lingered on a back field for a lengthy period and signed autographs for fans gathered near a chain-link fence.
"Everything, I enjoy it like it's the first day," Rivera said.
Rivera said that the recent retirements of Andy Pettitte and Posada, his "Core Four" teammates, had not made him think more about his own future. But Rivera acknowledged that he already has plans for life after he closes his final game for the Yankees.
He suggested that he might spend some time around the Minor Leagues with younger players, but Rivera listed his family and his church as two important areas of life that will also demand his attention.
"There's a lot of things more than baseball that I want to do," Rivera said. "It's just a matter of time."