Entering 2015, eight active quarterbacks (Tom Brady, Ben Roethlisberger, Peyton Manning, Eli Manning, Drew Brees, Aaron Rodgers, Joe Flacco, and Russell Wilson) will have Super Bowl rings to their names. That's one quarter of all starting QBs in the league.

In large parts of the NFL world, Super Bowl rings are synonymous with an "elite" label for quarterbacks, nevermind that a Super Bowl win is always a team achievement and not an individual achievement. By its very definition, "elite" status can only be afforded to a "select few", but when a quarter of all starting QBs have Super Bowl rings, that's not a "select few" anymore, and Super Bowl rings are no longer a valid measure of eliteness.

But that hasn't always been the case. Somewhere during the early stages of the Super Bowl era (Super Bowl I was played after the 1966 season, on January 15, 1967) the idea of the elite QB must have been born, and with it the notion that an elite QB had to have won a Super Bowl ring. And that notion held true throughout the 70s and 80s when only a select few QBs in the league were actual Super Bowl winners:

Between 1970 and 1991, there were never more than four or five active QBs in the league with a Super Bowl ring on their hand.

The number of SB-winning QBs rose to five in 1971 when Roger Staubach won his first Super Bowl ring. It stayed at five through 1977.

In 1978 it dropped back to four when Joe Namath retired after the 1977 season.

After Joe Theisman's Redskins won the 1982 Super Bowl, the number rose to five again, but dropped back down to four in 1984 after Ken Stabler retired.

It took another Redskins win in 1991 Super Bowl, this time with Mark Rypien under center, to move the number of active Super Bowl winning QBs to five.

In the 22 years between 1970 and 1991, ten years saw five active Super Bowl-winning QBs in the league, 12 years had only four Super Bowl-winning QBs active in the league at the same time. This relative scarcity of Super Bowl-winning QBs further solidified the idea that winning a Super Bowl (more specifically: playing on a team that won the Super Bowl) allowed a QB to join the ranks of the "select few" or "elite".

In 1992, the number jumped to six when Troy Aikman won his first Super Bowl with the Cowboys and joined the elite club. The number stayed at six until 1995, when it dropped back to five with the retirement of Joe Montana.



In 1996, Brett Favre joined the ranks of the elite and the number climbed back up to six QBs.

After the 1996 season, Jim MacMahon retired, but John Elway finally, finally got his ring to keep the number stable at six.

But when Mark Rypien and Jeff Hostetler both retired after the 1997 season, the number dropped back to four QBs, where it remained through the 2000 season.



So with the exception of four years in the mid-90's when there were six, there were never more than four or five Super Bowl-winning QBs in the league at the same time, regardless of how many teams the NFL had. But that changed in the new millennium. Here's how that number has increased over the last 15 seasons.

There are many reasons why the number of active Super Bowl-winning QBs has increased so dramatically. Player longevity, the salary cap, free agency, and other factors all play a role, but what the numbers ultimately mean is that using Super Bowl rings as a way to define elite QBs may have worked in the 70s and 80s, but today, where every Joe and Eli can win a ring or two, perhaps it's time to come up with a new way to define "elite".

One way of doing that, a way I discussed all the way back in 2010, is by quantifying "how much better a given quarterback was versus his peers who were playing at the same time." At the time, that kind of quantification required painstaking manual calculations, but today the fine folks at Pro-Football-Reference.com have automated that work. Here's how they calculate a QB's passer rating relative to his NFL peers in a stat called Passer Rating Index.

Passer Rating Index



For each NFL season, PFR compute two things:



The league average for that stat during the three-year period with the given year in the middle.



The standard deviation of the stat for all individuals who had 14 or more pass attempts per scheduled game during the three-year period.



Next, they compute how many standard deviations away from the league average each player was in each of his seasons. Then they multiply that number by 15 and add it to 100, and that is the number you see.



Reading the results:



On all stats, 100 is league average.

On all stats a higher number means better than average.

The greatest passing seasons of all time are in the 140s.

A typical league-leading season will be in the high 120s or the low-to-mid 130s.



You can review the Passer Rating Index (called "Rate+" in the PFR tables) for all QBs from 1955 through 2015 by following this link.

If you follow the link, you'll see that Aaron Rodgers (Passer Rating Index of 127), Steve Young (127), Joe Montana (123), and Roger Staubach (121) sit at the very top of the rankings, and there's little doubt in my mind that these guys were some of the best to play the game - in their time. Montana and Young played until they were 38, Staubach until he was 37, so we'll have to see whether the 31-year old Rodgers can maintain his place at the top of the table as he grows older, but for now he's one of the best to ever play the game.

Peyton Manning and Len Dawson, both with a Passer Rating Index of 120, sit just outside the top four. Dawson is in the Hall of Fame, Manning will soon be.

Next up is a trio of QBs who all share the same elite Passer Rating Index of 117, but have a widely divergent public perception: Tom Brady, Kurt Warner, and Tony Romo. In sum, these are the nine quarterbacks since 1955 whose passer rating has been one full standard deviation better than their peers over their entire career.

Other currently active QBs in the top 20 of that list are Drew Brees (115), Russell Wilson (115), Philip Rivers (114), and Ben Roethlisberger (113). That's it. Now let's go back to that list of Super Bowl-winning QBs and look at their career Passer Rating Index:

QB Passer Rating Index Aaron Rodgers 126 Peyton Manning

120 Tom Brady 117 Drew Brees 115 Russell Wilson

115 Ben Roethlisberger 113 Joe Flacco 100 Eli Manning 98

Obviously, it doesn't hurt to have a QB playing at an elite level if you want to win a Super Bowl. But it can also be done with average (Flacco) or below average (Eli) quarterbacks. The top six guys in the table above all rank among the Top 20 in Passer Rating Index since 1955, quite a remarkable feat. Sure, like Aaron Rodgers, some of the younger guys still have to show that they can maintain their play into their late thirties, so their numbers could potentially drop as they get older. But keep in mind that this Index is calculated versus the league average during each player's career, so you can't simply brush away these results because "the NFL has become a passing league."

For a QB to reach a value above 110, he'll have to have played a lot better than his fellow NFL peers, or his peers were a bunch of players like Rex Grossman (85), Mark Sanchez (87), Tim Tebow (88), or Sam Bradford (93).

Finally, just for fun, let's look at the most recent offseason QB ranking courtesy of Sports Illustrated, and see how the top 16 guys on that ranking look like when viewed via Passer Rating Index. And I'll preface the ranking by quoting Tom Ryle from this morning's news post:

Another offseason ranking. For those who aren't familiar with the official definition of "ranking" as commonly used in sports, it is "an extremely non-factual and highly opinion based listing, fully incorporating whatever misconceptions the author has".

Rank QB Passer Rating Index 1 Tom Brady 117 2

Aaron Rodgers 126 3

Andrew Luck

100

4

Peyton Manning 120 5

Ben Roethlisberger 113 6

Philip Rivers

114

7

Drew Brees 115 8

Joe Flacco 100 9 Matt Ryan 108 10

Tony Romo 117 11

Eli Manning 98 12

Russell Wilson 115 13

Matthew Stafford 98 14

Carson Palmer 104

15

Ryan Tannehill

97

16

Cam Newton 99

When you look at the SI.com ranking with the help of PFR's Passer Rating Index, you'll see some pretty average quarterbacks pretty far up the list, just as you'll see some pretty good quarterbacks pretty far down the list. As Tom said, that comes with the territory when you look at these types of rankings.

Former NFL linebacker Brady Poppinga, who played eight NFL seasons, including a four-game stint for the Cowboys at the end of the 2012 season, believes there can only be two or three QBs who can be considered elite.

"In my opinion, a truly elite player at the very least should be in the top 90 percentile of their respective group," Poppinga wrote on FootballByFootball.com. "That means at the most there are three quarterbacks who could be considered elite."

The Oxford Dictionary definition of elite is "a select part of a group that is superior to the rest in terms of ability or qualities". Based on their demonstrated ability as measured by the Passer Rating Index, Aaron Rodgers and Peyton Manning are truly elite guys among the currently active QBs, and they are followed by a whole bunch of QBs jockeying for a position among the elite ranks: Tom Brady, Tony Romo, Drew Brees, Russell Wilson, Philip Rivers, and Ben Roethlisberger.

If you want to elevate one of those guys into the elite group based on his Super Bowl rings, his draft pedigree, a few highlight plays, the strength of his defense, the number of commercials he appears in, or his hairstyle, then more power to you.