Why Mariano Rivera could be the first unanimous Hall of Famer

The game has never seen a postseason performer as fearsome as Mariano Rivera. Rich Schultz/Getty Images

Jackie Robinson is among the most important figures in our nation's history because of the change signaled by his Major League Baseball career, and yet he didn't come close to gaining unanimous election to the Baseball Hall of Fame the year he was voted in. He was left off of 36 of 160 ballots. Willie Mays was somehow left off of 23 of 432 ballots. Hank Aaron retired as the all-time home run king, and he was omitted from nine of 415 ballots.

Nobody has ever been named on every ballot, although Ken Griffey Jr. came very close a few years ago, when he was included on 437 of 440 ballots.

But it appears that former New York Yankees closer Mariano Rivera has a legitimate shot. The conditions are ripe for a 100 percent voting record, although it's very possible that some writer already has decided to not include Rivera on his or her ballot. But what are the reasons why?