Update Friday 5:45 EDT: Mariano Rivera answers one question, tweeting:

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

He also told reporters in Kansas City “I’m not going out like this.” The under-covered part of this story is not the torn ACL but the addition of the meniscus damage, which Rivera originally knew about, but the Yankees did not. Interestingly-timed piece in the New York Daily News.

Original Post:

At the risk of further turning major league baseball pitchers into the equivalents of the pampered and petrified thoroughbred race horses – don’t the Yankees have somebody to shag fly balls forMariano Rivera?

In considering the implications of his likely torn Anterior Cruciate Ligament in his right knee, it is important to remember that since his days in the low minors, Rivera has included in his pre-game routine fairly vigorous pursuit of batting practice shots. But something then-manager Joe Torre said in 2006 is just as important. Somebody was looking at the Yankees’ lack of outfield depth and wondered if Derek Jeter might be an option in center, and Torre noted that while Jeter would survive there, the man on the team who was easily his best defensive center fielder was Rivera.

Torre’s observation was spoken seriously – Rivera has a great ability to read a fly ball, and is a terrific athlete – but it was not supposed to be taken seriously. But the New York newspapers did, and I actually called Torre to ask him about their extrapolations that this was a hint that Rivera was now somehow the greatest closer of all time and an emergency outfielder.

“Yes, he’s a great outfielder,” Torre said, “He’s always bugging me to let him play there in a game. But does anybody really think I’d be crazy enough to let him play in a game? What if he got hurt?”

Tonight we know the answer. After his pre-game injury sustained trying to chase down a fly off the bat of brand-new Yankee Jayson Nix, Rivera underwent an MRI, and after the Yankees’ 4-3 loss in Kansas City, manager Joe Girardi told reporters that the Royals’ team doctor said he thought the imaging indicated a torn ACL. Any tearing injury to that knee ligament would be severe enough to end Rivera’s season and, at his age, perhaps to his career. “If that’s the report,” Girardi told reporters in a media gaggle carried on the Yankee-owned YES network, “that’s about as bad as it gets.”

Did Rivera’s luck just run out? Did the luck of all pitchers just run out? Will they no longer be allowed to do anything unnecessary on the field? Girardi, whom the New York Times noted got the same ‘put me in coach’ pleading from Rivera as Torre had, thought not: “You can fall off a curb and get hurt. You have to allow him to be an athlete and be a baseball player and have fun out there. I’ve never seen Mo do anything recklessly, I’ve never seen Mo dive or try to rob a home run. It’s one of the way he exercises.”

But the disturbing, harrowing video of Rivera’s injury suggests he was in fact doing something that could be considered reckless, or at least slightly so. Just before his knee buckled, Rivera can be seen stretching his glove arm back over his body in a way he would not ordinarily do during a game, while simultaneously leaping. Can you trust pitchers not to jump, not to feel they have to catch that fly ball that’s just out of their grasp? Can you trust 42-year old future Hall of Famers not to?

Rivera told reporters in Kansas City that if he had to be injured, at least it happened while he was doing something he enjoyed. “Shagging, I love to do. If I had to do it all over again, I would do it again. No hesitation.” He confirmed that “it’s torn” and added a detail Girardi did not mention “meniscus also.” It’s unclear the extent of any injury to the meniscus. Rivera said he had no idea if he would pitch again.

But there is a responsibility to balance a player’s rituals and athleticism – and fun – and the inevitability of the clock running out. Decades ago, the Yankees moved Mickey Mantle from center to first base in hopes of preserving his knees and his career a season or two more. Even now Joe Mauer’s future – catcher, first baseman, or outfielder – is debated.

And with time, we reassess what a player should and should not be allowed to do. Jim Lonborg helped to pitch the “Impossible Dream” Boston Red Sox into the World Series, and won the 1967 Cy Young Award. That winter he tore up a leg while skiing, and soon player contracts began to be peppered with clauses prohibiting them from participating in dangerous sports. 26 years later, Texas Rangers’ manager Kevin Kennedy acceded to Jose Canseco’s wishes and let him throw 33 pitches in a blowout game against the Red Sox at Fenway. By the end of another incidence of letting a player do what he wanted, the blowout was in Canseco’s elbow and he would require Tommy John surgery. And just this past winter, the New York Mets made it clear that pitcher R.A. Dickey could go ahead with his plan to climb Mount Kilimanjaro, but if he were injured, they would exercise their right to void his contract.

Girardi is right: Shagging flies has always been integral to Rivera’s pre-game routine, his exercise regimen, and his simple enjoyment of baseball. But that doesn’t mean it was the right thing to do, nor the smart thing – just that nobody this good had previously sustained a potentially career-threatening injury. And Joe Torre’s rhetorical question about what would happen if Rivera were injured playing center underscores another essential element. If it had happened that way, it would at least have happened in a game, presumably for some vital or unavoidable reason, and not because a future Hall of Famer just had to throw himself off balance because his competitiveness demanded that he go all out to catch a batting practice fly ball.

With Rivera’s career potentially over, will teams try to curb their pitchers’ non-essential on-field activities? The answer may lie in another question: When Kendrys Morales of the Angels sustained a devastating fractured ankle during a team celebration after his walk off grand slam two years ago this month, didn’t we all assume we had seen the end of the ‘group jump’?