Favre's longevity, durability set him apart

Was Brett Favre the greatest quarterback in NFL history? Yes -- and no.

Your opinion depends on what it means to be the "greatest of all time." Are we talking about the quarterback who had the greatest four- to five-year peak, during which he dominated the game? Or are we talking about the quarterback who gave his team the most value over an entire career? Most of the time, when we talk about the greatest players ever, we sort of fudge the question, not judging on either criterion but rather smushing the two together.

When Bill James rated the greatest baseball players ever in his original "Historical Baseball Abstract," he chose a different route; James created two completely different lists, one for peak value and one for career value. That's also how we have to look at Favre's place in NFL history.

Best-Ever Debate

In his 17 seasons, Brett Favre set numerous NFL records, including most yards passing (61,655) and touchdowns (442).

But do those numbers, combined with Favre's three MVP awards and one Super Bowl victory, put him among the top 10 quarterbacks of all time?

Recently, ESPN.com's Mike Sando examined this debate. While seven seasoned evaluators placed Tom Brady solidly in the top 10 quarterbacks of all time, Johnny Unitas consistently ranked higher than any other QB.

Favre won three straight MVP awards in the mid-1990s (one shared with Barry Sanders), but that three-year period doesn't even come close to ranking as the greatest three-year performance by an NFL quarterback. At the same time, there aren't many quarterbacks who played as well, for as long, as Favre.

In my book, "Pro Football Prospectus 2005," I published a long statistical analysis of the greatest quarterback seasons in modern NFL history. (It actually started as an ESPN.com piece, which you can read here.) Not a single Favre season finishes in the top 50, and only one (1995) ranks in the top 80. By comparison, Johnny Unitas, Roger Staubach and Peyton Manning each have four seasons in the top 50 (including one Manning season since the book was published). By including both rushing and passing performance, Steve Young comes out with four seasons in the top 20.

Favre's best seasons don't rank among the best of all time because his completion percentage just wasn't good enough. Favre set a career high in completion percentage (66.5 percent) his final season, and he never ranked in the top five in completion percentage during his peak years of 1993 through 1997 (although he led the league in 1998).

Of course, Favre didn't have a spectacular completion percentage because Green Bay's offense was built on high-risk, high-reward deep passes. Although Favre completed enough of those deep passes to be the best quarterback in the league at the time, he didn't complete enough for those seasons to count among the greatest ever.

In his best season, 1995, Favre completed 63 percent of his passes with 12.3 yards per completion. Since 1960, 24 different quarterbacks had at least one season in which they ranked higher in both statistics, including Young four times and Kurt Warner three times.

Favre also threw more interceptions and was sacked more frequently than many of the other great quarterbacks in their best years, and most of his best seasons (with the exception of 1996) came against a schedule of defenses that were below average.

For most of his career, Favre was very good, but not spectacular. What's spectacular is just how many of those "very good" seasons Favre had. Of course, Favre set all of the all-time passing records over the past two seasons, but what is impressive is that he didn't set those records by sticking around as a mediocre quarterback long after his time had passed. Based on our numbers, Favre had more value in his final season than every quarterback in the league except for Tom Brady and Manning.

At Football Outsiders, we use our complex DVOA (Defense-adjusted Value Over Average) metric to break down every single play of the season and figure out how good each player is compared to the average player at his position. Our play-by-play database goes back to 1995, so it includes most of Favre's career. Only once, in 1999, does Favre come out as a below-average quarterback -- and just barely.

In 2005, Favre threw a league-leading 29 interceptions, and most observers believed he had hit the end of the line. Yet even that year, Favre was an above-average quarterback when you consider his team's schedule. Green Bay played six games that season against the four defenses with the most interceptions -- Cincinnati, Chicago, Minnesota and Carolina -- and another two games against Detroit, which ranked seventh.

If we assume that Favre was above-average in his first three seasons as a starter -- a fairly safe assumption -- that means he gave the Green Bay Packers 15 years of above-average play at the game's most important position -- and he did so without missing a game after taking over the position in early 1992.

Compare that to the other quarterbacks who are considered to be among the best ever. Joe Montana was injury-prone for the second half of his career. Unitas struggled once he got into his mid-30s. Young had the greatest peak of any quarterback in history, but he played only nine seasons as an NFL starter. Staubach started for only eight.

Combine quality and longevity, and the only quarterbacks who can compare to Favre are John Elway and Dan Marino. Many fans would say that the greatest quarterback career in history would have to include at least one championship, and that would narrow it down to Elway and Favre.

As to which of those two men had the greatest quarterback career in history, well, we'll let the Denver and Green Bay fans fight it out for the next 10 years. At some point, Manning and/or Brady may pass them both, but nothing guarantees that Manning and Brady will stay consistent and healthy throughout their 30s. Not many quarterbacks do, and that's what made Favre unique.

Aaron Schatz is president of Football Outsiders Inc. and the lead author of Pro Football Prospectus 2007 and 2008.