Pitch after pitch, game after game, year after year, Rivera has exhibited the personal know-how and self-awareness to -- in Chamberlain's words -- "just be Mo."
"His delivery, he repeats it every time," Chamberlain said. "He knows when his arm gets out of slot. He knows what he has to do right there. That's the difference with the good ones -- he doesn't need anyone to come tell him."
Rivera recorded the 450th save of his illustrious career on Sunday at Progressive Field, hurling a perfect ninth inning with two strikeouts to preserve a 1-0 Yankees victory over the Indians. Entering Monday, Rivera had not allowed a run or a walk in nine appearances this season, recording seven saves and striking out 10 batters in 10 innings.
"It's a blessing to have the opportunities, and you have to be blessed to pitch that long to achieve [450 saves]," Rivera said. "It's not about numbers. It's about having the opportunity to help the team, because without having my teammates to give me the opportunities, I would never have that."
Rivera's 450 saves are the most in the history of the American League and third most on baseball's all-time list, trailing Trevor Hoffman (528) and Lee Smith (478).
Yankees manager Joe Girardi called the accomplishment "awfully big," considering that Rivera didn't even begin life as a closer -- he came up as a starting pitcher and then served as a setup man to John Wetteland on the Yankees' 1996 World Series-winning club, for which Girardi caught.
"He's just so consistent," Girardi said. "Mo is one of those guys that what he does doesn't really faze you. You see how good he's been and you're never really surprised by any accomplishment that he reaches."
Compared to last April, Rivera's dominance has made for an even more striking comparison. Rivera did not record his seventh save of 2007 until the Yankees' 58th game, on June 7 at Chicago.
He blew his first two save opportunities of that campaign, serving up a three-run homer to Oakland's Marco Scutaro last April 15 and allowing three runs to the Red Sox in two-thirds of an inning on April 20 at Fenway Park.
Rivera believes the key for him has been finding more regular work, allowing him to remain sharper.
"Last year, I didn't pitch at all almost in the first month," Rivera said. "Now, I have a little bit more opportunities. If you have them, you take advantage of them. I don't compare seasons to other seasons. Last year was last year. That's the way I go about business."
As his plaque in Cooperstown, N.Y., will almost surely attest one day, Rivera enjoyed his success primarily on the strength of one pitch, his cutter. Chamberlain called it "the best pitch in baseball," and having that weapon in the arsenal makes life on the job that much more enjoyable for the Yankees' catchers.
"You know the game is going to be over soon, because he's going to make it end," Jose Molina said. "You have to like that mentality. He's been around a long time, and he has that perfect movement and that perfect location."
Though everyone from the batter's box to the upper deck knows pretty much what Rivera is about to throw -- he has toyed with other pitches, but Molina said that he has called almost 100 percent cutters for Rivera since joining the team last July -- it still proves effective. Therein lies the magic of Mariano.
"You [reporters] may call it just one pitch, and the fans may think he has just one pitch," Molina said. "To me, he has seven pitches, something like that. I can call for it up, down, inside, outside, wherever we need it. We're on the same page."
"I don't care how good your curveball, changeup or slider are," Chamberlain said. "At 92, 95 and 96 [mph] sometimes, it's not going straight. That all comes down to his delivery."
Now 38 and in the first season of a three-year, $45 million contract, Rivera said that he has enjoyed the opportunity to help influence the minds of some of the Yankees' relievers.
Television cameras often catch Chamberlain and Rivera spitting sunflower seeds in the bullpen and shooting the breeze, and though Rivera doesn't pop the mid-90s nearly as often as Chamberlain does, he hopes to provide some even more valuable ammunition for the 22-year-old setup man than just plain octane.
"I want to be able to be there for them and make sure that I put something good in their minds," Rivera said. "I want them to be able to pull something out of their minds when they need it and put it to work. I like to help. I like to do good. I don't want to do something halfway. I want to do my best."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.