Rounding Third: Exit Sandman: Is this how it ends for Rivera?

This wasn't supposed to be how it ended for Mariano Rivera.

While most assumed this was going to be the great Rivera's final season, the reality of it all may have set in on Thursday night when the future Hall of Famer tore the anterior cruciate ligament in his right knee, thus ending his season and perhaps the career of the greatest reliever to ever appear in a Major League Baseball game.

It's almost too crazy to believe, especially when you consider how it happened.

Prior to the Yankees' 4-3 loss in Kansas City, Rivera was shagging fly balls during batting practice, something he has done almost every day of his 18-year career. He lunged for a ball hit by Jayson Nix near the warning track in left- center field when his knee buckled and he lost his footing. He immediately clutched at the knee and was writhing in pain.

"I grabbed myself between the grass and the dirt. I couldn't pull my leg up and twisted it (the knee). It's an ACL. Torn actually. Meniscus also," Rivera said.

With concerned teammates looking on, manager Joe Girardi jogged to the outfield wall with members of the training staff to attend to Rivera, who was placed onto a flatbed truck and carted back around the diamond.

"He broke for a ball like he always does, and then it kind of went funny," said Yankees pitcher David Robertson, who saw the injury up close. "At first, I thought it was funny -- and then all of a sudden I realized he was injured, he was down. That's when I really got worried. There's nothing I can do except stand there and watch. It's a miserable feeling."

By the way, for anyone who wants to kill Girardi for even having him out there, get a clue. Rivera actually took pride in his work in the outfield before games, often commenting that his dream was to play center field before he retired.

It was a freak accident. It happens.

Now we have to wonder if this is it. Does Rivera's career end with him being carted off the field? When he announced in spring training that he already knew his decision concerning his future, I assumed, like most, that this was probably it.

I mean what more does he have to prove. He's won five World Series titles, he has the all-time saves record and is quite possibly the most respected player in the league.

There is nothing left for him to prove.

But, this isn't on his terms. I'd find it hard to believe that this is the sendoff he envisioned. Dollars to doughnuts, Rivera is back for one more season.

So, where do the Yankees go from here?

For the past few years, Robertson has been considered the heir apparent, especially after his spectacular All-Star season of 2011 that saw him pitch to a 1.08 ERA with 100 strikeouts in 66 2/3 innings of 70 games.

He'll be given first crack at it, but should he falter the team also has another former closer on their roster in Rafael Soriano, who will now become the team's eighth-inning pitcher. And don't be surprised if Phil Hughes finds his way back to the pen once Andy Pettitte is ready to step into the rotation, perhaps as soon as next week.

Luckily the Yankees have bullpen depth and are in better position to deal with this than most other teams. But you can't replace Rivera. Robertson and Soriano will probably be fine, but they'll never be Rivera. That's not a knock on them. There will never be another Mariano Rivera.

"Mo is a vital part of this team on the field, off the field. He's going to be missed," Yankees captain Derek Jeter said. "There's no other way to put it. You don't replace him. Someone else can do his job, but you can't really replace him."

I've long argued that Rivera is not only the best closer to ever play the game, but he is best player of his generation. Understandably it's hard to justify that for a player who appears, for the most part, one inning a night, 60 times a year.

But if you can find me a more dominant or important player in this era than Rivera, go right ahead.

The stats on Rivera are mind-boggling. His 2.21 lifetime ERA is the second- lowest in history for a pitcher with more than 1,000 innings, since ERA became an official statistic in 1913.

Actually the more amazing thing about that is that Babe Ruth is fourth on the list.

As impressive as the 608 regular-season saves are for Rivera, it's the 42 that he has in the postseason that separates himself from just about anyone who has ever pitched in October.

Comparing Rivera to anyone in the postseason, though, is ridiculous. It's his domain. He's appeared in 96 games and has pitched to a 0.70 ERA. He's so good that his blown saves have become actual events. He has thrown 141 postseason innings with just one loss.

That's right, one loss. He's about the closest thing to automatic as there has been.

And if in fact this is it, mark your calendars for July 22, 2018, because that's the day he'll be inducted into the Hall of Fame. It's not a question of if he gets in, the only question is will he receive more votes than any player? Nolan Ryan currently holds that distinction with 491 votes, while Tom Seaver has the highest percentage of votes, as he was named on 425 of 430 ballots.

Rivera may challenge both. One because he was that good and two there may not be a player who was more respected and revered by the media simply because he doesn't show anyone up and treats his opponents with the same respect he shows his teammates.

Former Minnesota Twins manager Tom Kelly may have had the best quote of all- time when describing Rivera.

"We don't want to face him anymore," Kelly said. "He's too good. He belongs in a higher league. He should be banned from baseball."

Let's hope Rivera gets to leave on his terms.