NEW YORK -- It has long been an established fact that Mariano Rivera is a human being.
If there were any lingering doubts about that, Mo allayed them Sunday night in Boston, and in case anyone wasn't paying attention, again on Tuesday night right here against the Angels.
And it just as established that, since he is a human being, he is not perfect. If we can all live with our own imperfections, we can certainly live with Mo's.
But three consecutive games of imperfect humanity?
Say it ain't Mo!
The Yankees didn't lose because of Mariano Rivera on Thursday the way they did Tuesday night, and they didn't have to go to extra innings, where they wound up losing, because of Mariano Rivera, as they did on Sunday.
They survived Mariano's latest bout of imperfection, winning 6-5 over the Los Angeles Angels at Yankee Stadium despite Mo making it, er, interesting by serving up a three-run homer to Russell Branyan on the first pitch he threw in the ninth inning.
So it was easy, once again, for Joe Girardi and Derek Jeter and Robbie Cano, the game's hitting star, and Mo himself, to shrug this one off as just another example that every so often the greatest closer this game has ever known can become rather ordinary.
No doubt, Rivera has had stretches like this before, and has always bounced back from them. As recently as last September, Mo blew three of his last seven regular-season save opportunities. Then, in the playoffs, he didn't allow a run in 6 1/3 innings in six appearances.
So you can't blame Mo's manager or his teammates or Mo himself for dismissing his current struggles as just one more bump in a road that has mostly been as smooth as the Autobahn.
But what if it isn't? What if this truly is the beginning of the end, because everything, good and bad, eventually must come to an end.
On Nov. 29, Mariano Rivera will turn 42 years old. That is seven years older than Bruce Sutter, the first closer to go to Cooperstown, was when he retired. It is five years older than John Franco was when he was done as a closer. It is three years older than Lee Smith, for years the all-time saves leader with 478, was when he retired.
It is six years older than Goose Gossage, a Hall of Famer and the greatest closer the Yankees ever had pre-Mo, was when he was washed-up closing games. Past the age of 36, Goose had just 13 more saves spread over six seasons.
And Trevor Hoffman, the man Rivera is chasing for the all-time saves record -- he is 12 short of Hoffman's 601 -- absolutely fell off the cliff as a 42-year-old, dropping from 37 saves and a 1.83 ERA in 2009 to 10 saves and 5.89 ERA in 2010, to retirement in 2011.
Only Dennis Eckersley, another Hall of Famer, got as many as one save after his 43rd birthday. And that is all he got, one, in 1998, with the Red Sox.
Rivera, of course, is better than all of them, but in one very important respect he is every bit the same. Like all of them, he too is human and subject to the ravages of the aging process.
Already this season, we have seen him miss four games after suffering soreness in his right triceps after blowing a save to the Mets on July 3. At that time, he not only acknowledged the pain, he said that arm discomfort was something he would have to live with, and play through, for the rest of his career.
After Thursday's game, he insisted everything is OK physically, that the triceps soreness was gone. He said there were no mechanical problems for him to work on and no psychological barriers to hurdle. Nothing at all but bad pitch location on one pitch in one inning of one game.
It just happened to be the first one he threw after being summoned when Cory Wade couldn't close out a 6-2 game after Cano's grand slam in the seventh had broken a 2-2 tie.
"It's one pitch," he said. "It's not like I've been missing, missing and missing. You throw one pitch up there, that's the difference."
It was one pitch Thursday and one pitch Tuesday, when Bobby Abreu hit one out in the ninth to win a game, 6-4, for the Angels, and a couple of pitches on Sunday, one that Marco Scutaro lined off the Green Monster and another that Dustin Pedroia lined deep to right to score the tying run and enable the Red Sox to pull out a 3-2 win in 10 innings.
It could mean nothing, or it could mean everything.
So when does it become an area of legitimate concern?
"If it happened for a month," Girardi said, only half-joking. "I've seen Mo have three or four bad days and then run off a long streak. I don't think that all of a sudden Mo's forgotten how to pitch. He's in a little blip on the radar screen and he'll get back on track. As much as we want to think he's as close to the perfect closer as we have ever seen, he's not perfect. Fortunately it didn't cost us today, and we move on."
That's all true, but so is this: When a player has been as great for as long as Mariano Rivera has been great, it is easy to write things off as blips on a radar screen or bumps in a road.
And by the time you realize what you thought was a blip is actually an impending collision or what you assumed was a pothole is actually the end of the road, it is too late to do anything about it.
We don't profess to know if this is just another of Mariano's occasional slumps or the beginning of his decline. We just know that it is wise to hope for one but be prepared for the other.
"He can't be perfect all the time," Jeter said. "I mean no one's perfect all the time. I don't worry about him. We won the game."
Mo, too, maintained that he was not worried, but as he watched Abreu's shot leave the park on Tuesday, his face wore a look of utter disbelief. On Thursday, as he followed the arc of Branyan's blast, that expression had been replaced by one of resignation.
"Nobody likes this," he said. "Nobody wants to go out there and give up the game, and throw pitches that let up home runs. Games like this get me upset, because I'm not doing what I'm supposed to be doing."
Mariano Rivera is not supposed to be fallible, or vulnerable, or human.
But he is and always has been all three, and this week, he has reminded us of that again. And again. And again.