Let’s start with Bradshaw and begin by looking at his Relative ANY/A for each year of his career. For new readers, ANY/A stands for Adjusted Net Yards per Attempt, defined as

Relative ANY/A simply compares a quarterback’s ANY/A average to league average, a necessary element when comparing quarterbacks across eras. In the graph below, the size of the bubble corresponds to how many attempts Bradshaw had in each season, while the Y-Axis shows Bradshaw’s Relative ANY/A (by definition, 0 is equal to league average).  The graph shows a clear story: for the first five years of his career, Bradshaw was a below-average quarterback, but over the rest of his career, he was one of the best in football. His best year came in 1978 when Bradshaw finished with a RANY/A of +2.0, which was the third best mark in football (only a hair behind Roger Staubach and Dan Fouts). Those stats, combined with a 14-2 record, led to Bradshaw being named the AP’s MVP that season.

Now, let’s do the same for Warner. We can see that he had several years with low pass attempts numbers — mainly 1998, 2003, and 2006 — but what really stands out is the odd shape of his career.  His best RANY/A years were his first, as the chief executive officer of the Greatest Show on Turf.  But from 2002 to 2006, Warner never started more than 10 games in a season (due to injuries, Eli Manning, and Matt Leinart), although his RANY/A was good the last three of those seasons.  Later on, like Bradshaw, Warner retired while still being a solidly above-average passer.

The reason to use RANY/A and not ANY/A is that by adjusting for era, we can compare apples to apples. So let’s combine our two bubble graphs and look at Warner’s and Bradshaw’s careers together, with the X-Axis now showing “year of career” instead of simply year.

Early on, Warner was the much better passer, but that edge doesn’t hold up for very long. Once we move past Warner’s scorched-earth GSOT days — where, admittedly, Bradshaw simply can’t compare — the old Steelers quarterback holds the edge for the remainder of their two careers.

After the era adjustment, Warner still holds an edge due to his run from 1999-2001 but there are other adjustments to be made. Consider that Warner played nearly his entire career in the NFC West when that division was one of the worst in football. As we’ll soon see, a strength-of-schedule adjustment will narrow the gap between these two quarterbacks.

But first, I’m going to make another adjustment that will put Bradshaw in a more positive light. I’m going to exclude his horrendous rookie season, which drags down his career averages considerably. Is that fair? I leave that up to the reader to decide. Bradshaw was the number one overall pick in the draft, while Warner went undrafted in 1994, was cut from Packers camp that same year, played in the Arena Football League for four seasons, and made it on to the 1998 Rams as the third stringer. In that context, I think it’s fair to give Bradshaw a pass for miserable stats at age 22 when he was handed the starting job even though he clearly wasn’t ready to play, since Warner’s career stats don’t reflect his level of play at a young age.

Like all players, Bradshaw's performance must be judged in the proper context.

So after adjusting for strength of schedule and era (and removing Bradshaw’s rookie year), we get a much different picture. Remember, the raw stats show that Warner had a career 7.55 AY/A average, while Bradshaw was at just 5.83, which results in a large difference of 1.72 Adjusted Yards per Attempt. But after these adjustments, Warner comes out as just 0.38 AY/A ahead of Bradshaw. We can quantify exactly how much of that gap was closed by each adjustment: most of it comes from the era adjustment (+0.89), with the rest split between eliminating 1970 from Bradshaw’s line (+0.22), and the SOS adjustment (+0.23).

But we’re not done yet. We have acknowledged that Warner played in a much more pass-friendly environment, that he wasn’t put on the field as an unprepared 22-year-old, and that he had an easier schedule. But Warner also benefited from playing the majority of his games in a dome or in Arizona’s retractable-roof facility. I looked at Warner’s and Bradshaw’s statistics in dome games, in outdoor games, and in games with half-domes or retractable roofs (for Bradshaw, this consists of two games in Dallas; for Warner, it’s his games in University of Phoenix Stadium, and one game each in Dallas and Houston). Here’s how to read the table below. For Warner, he had 1,246 regular season pass attempts in domes. His Expected AY/A based on the defenses he faced was 6.84 (this is the combined SOS/era adjustment), while he actually averaged 8.98 AY/A. Therefore, in dome games, Warner averaged 2.14 AY/A over expectation.

Warner was much, much better in dome games than he was outside, and that must be part of the discussion when comparing him to a player like Bradshaw. Now remember — and this is something the Peyton Manning detractors often forget — the numbers here overstate the advantage Warner gained from playing in a dome. That’s because nearly all of his outdoor games were road games (and most of his dome games were home games), where we would expect his AY/A be lower. And we must remember that most of Warner’s dome games came when he had the best supporting cast of his career, so the high average in dome games is largely a result of having Marshall Faulk, Orlando Pace, and the rest of the one of the most talent-rich offenses ever. So it would be wrong to look at this table and say playing in a dome made Warner. For Bradshaw, his performance in dome games all came on the road, of course, with the vast majority coming in the Astrodome against the Oilers. But in outdoors games, he provided +0.85 AY/A better than expectation.

So where does this leave us? It’s up to the reader to decide which is more impressive: being +1.02 AY/A better than average with 47% of your passes coming outdoors, or +0.64 AY/A better than average with 90% of your passes coming outdoors. Certainly some penalty must be given to Warner since his numbers came in friendly environments and he was far from dominant in outdoor games. One must also remember that Bradshaw wasn’t just playing outdoors: a fair number of his games were in cities like Pittsburgh, Cleveland, and Cincinnati in November and December, which probably provided worse conditions than the average Warner outdoors game, too.

For me, the journey here is more important than the destination. On the surface, Warner’s career stats look significantly better than Bradshaw’s. But the entire point of the analytics movement is to put statistics in proper perspective. After adjusting for era, strength of schedule, different career arcs, and weather, we can see that their numbers look very similar. And honestly, that’s how it should be, since we’re talking about two Hall of Fame caliber quarterbacks. Much of football analytics can be shortened to “putting everyone on the same playing field.” The idea that analytics can’t solve everything is true, but this is still a much better method of comparing quarterbacks than simply throwing out the stats because you can’t judge quarterbacks from different eras.

We must also remember that determining which quarterback was better involves a different level of discussion than what is in today’s post, where I simply compared their statistics in the proper light. In a broader debate, you’d also want to include playoff performances. In this regard, both were outstanding: I ranked Bradshaw number two and Warner number four on my Super Bowl era list of best playoff passers. You’d also want to take into account the supporting cast of both players, although again, both have similar arguments here. Bradshaw had Hall of Fame caliber receivers in Lynn Swann and John Stallworth; Warner had that in St. Louis (Isaac Bruce and Torry Holt) and in Arizona (Anquan Boldin and Larry Fitzgerald). I encourage you to discuss in the comments which quarterback you think was better, along with your thoughts on this method of analysis.

No, Peyton, you're the man.

When the greatest quarterback seasons of all time are discussed, these three years dominate the discussion. And with good reason. But if you include the playoffs — and frankly, there’s no reason not to include the playoffs — which quarterback produced the greatest season of all time? I’m going to stipulate that the greatest quarterback season ever has to end in a Lombardi Trophy, because otherwise, I think we’ll end up back in the world of Marino ’84/Brady ’07/Manning ’04. Of course, now another Manning season has entered the mix: and with a Super Bowl win, Manning’s 2013 should and would be remembered as the greatest quarterback season of all time.

So, the question becomes, which season would he knock off the top rung? I think there are six seasons that stand out from the rest, based on regular and postseason performance.

Honorable Mention

Both of these guys had some good years.

Terry Bradshaw, 1978: Was named AP MVP for his outstanding regular season, although it was not a transcendent year by historic standards. Had a magnificent postseason, culminating in a 300-yard, 4-TD performance against the Cowboys in Super Bowl XIII.

Joe Montana, 1984: Marino’s record-setting year and San Francisco’s general dominance en route to a 15-1 regular season obscured how dominant Montana was this year. But his postseason was not stellar — he threw 5 interceptions in wins against the Giants and Bears.

Troy Aikman, 1992: Younger fans may wonder why Aikman was held in such high regard by his peers. By today’s standards, most of his numbers look pedestrian. But no one could say that about his performance in the three playoff games in 1992 that handed Dallas its first Super Bowl title of the ’90s: 61-89, 795 yards, 8 touchdowns, 0 interceptions, 126.4 passer rating, 9.50 ANY/A.

Aaron Rodgers, 2010: Rodgers’ magnificent 2010 postseason set the table for his otherworldly 2011 season. Still, he was very good in the 2010 regular season, when he ranked in the top 3 in passer rating, NY/A, ANY/A and also rushed for 356 yards and four scores. In the playoffs, he threw 9 touchdowns and ran for two more, while posting a 109.8 passer rating on 132 passes.

Eli Manning, 2011: Threw for over 6,000 yards including the playoffs, as the Giants ranked last in rushing yards. The 2007 season was fluky, but the 2011 season was full of legitimately great quarterback play from the younger Manning.

Joe Flacco, 2012: Completely uninspiring during the regular season, but arguably one of the top two greatest quarterback postseasons ever.

#6) Mark Rypien, 1991

Rypien led the league in yards per completion, Adjusted Net Yards per Attempt, and game-winning drives. Washington started 14-1 before losing a meaningless week 17 finale, and that team is widely considered one of the greatest ever. Rypien posted a Relative ANY/A of +3.2 (meaning he averaged 3.2 ANY/A more than league average), although part of the credit goes to a dominant offensive line and some excellent skill-position talent (Gary Clark, Art Monk, Ricky Sanders, and Earnest Byner). The running game and defense handled Atlanta in Washington’s first playoff win, but Rypien starred in an NFC Championship Game blowout by throwing for 228 yards and 2 touchdowns on just 17 pass attempts. In the Super Bowl, Rypien went 18/33 for 292 yards and 2 touchdowns with one pick, and was named Super Bowl MVP. This was a marvelous season that isn’t commonly celebrated for one reason: Rypien isn’t a Hall of Fame caliber quarterback.

#5) Bart Starr, 1966

Remembered by some as a game manager, Starr never posted Johnny Unitas numbers (i.e., Star Wars numbers)…. that is, until 1966. That year, the Packers great was named MVP by the AP, UPI, and NEA after leading the 16-team NFL in completion percentage, interception rate, yards per attempt, and passer rating. At the time, Starr’s 105.0 passer rating was the third best in NFL history. He posted a Relative ANY/A of +3.8, still one of the top 10 averages since 1950. Then, in the NFL title game in Dallas, Starr was magnificent with numbers that would be outstanding in 2014: 19/28 for 304 yards, 4 TDs, 0 INTs. Then, Starr followed that up with a 16/23 for 250 yards, 2 TDs, and 1 INT stat line in the first Super Bowl. It’s hard to believe this only ranks 5th.

#4) Drew Brees, 2009

In many ways the anti-Starr, Brees finally shed the “stats star” label by winning Super Bowl XLV. That capped a marvelous season in which he posted an ANY/A of 8.31, the best of his outstanding career. Brees led the NFL in completion percentage, touchdowns, touchdown rate, passer rating, and ANY/A. His Relative ANY/A was “only” +2.7, but Brees had 534 dropbacks (Starr in ’66 had just 275). Few champions have been built almost entirely around the quarterback like the 2009 Saints, which is why I’ve got him at number four. In the playoffs, Brees was flawless: he completed 72 of 102 passes for 732 yards with 8 touchdowns and no interceptions. Brees posted a passer rating of over 100 in each of his three playoff games, all of which came against likely Hall of Fame quarterbacks: Kurt Warner, Brett Favre, and Peyton Manning.

#3) Kurt Warner, 1999

Warner remains the last player to win the AP MVP and the Super Bowl in the same season. In 1999, he led the NFL in completion percentage, touchdowns, touchdown rate, yards per attempt, AY/A, NY/A, ANY/A, and passer rating. He very nearly led the league in passing yards, and likely would have if he didn’t sit for much of week 17 (he finished less than 100 yards behind Steve Beuerlein). The Rams All-Pro became just the second player to ever throw 40 touchdowns in a season. The only knock on Warner was a mistake-filled postseason. And while he threw four interceptions in three games, he still managed to post a 100 passer rating over three games, thanks to an 8.8 Y/A average and 8 touchdowns.

Owners of the two greatest quarterback seasons ever -- for now.

Young was absurdly efficient almost every season in the ’90s, but 1994 was his masterpiece: he won the AP MVP and led the NFL in completion percentage, touchdowns, touchdown rate, yards per attempt, AY/A, NY/A, and ANY/A. His 112.8 passer rating set a new NFL record, eclipsing the mark set by his former teammate, Joe Montana. And Young also ran for 7 touchdowns! Close to a perfect season for the 49ers Hall of Famer then turned into a fantastic postseason, where he threw 9 touchdowns (and ran for two more) and no interceptions. It’s hard to top this season, but…

#1) Joe Montana, 1989

Montana had a Relative ANY/A of +3.1 in ’89 (which does edge Young’s +2.9 in ’94), but that only tells part of the story. The 49ers won the Super Bowl in 1988 but were even better in ’89. Montana completed 70.2% of his passes, an absurd number for that (or any) era. The former 49ers star also led the league in touchdown percentage, yards per attempt, AY/A, passing yards per game, passer rating, NY/A, and ANY/A. The only knock was he missed three games, but his stellar postseason performance is enough to overcome that flaw. Compared to the league average ANY/A of 5.24 in 1989, Montana provided 570 Adjusted Net Yards over average, the most ever in a postseason (Flacco 2012 is second at 539). In English? Montana completed 78% of his 83 passes for 800 yards, 11 touchdowns, and no interceptions. He went 26/30 for 262 yards and 2 touchdowns in the NFC Championship Game, and that was his worst playoff game. A dominant regular season and the greatest playoff stretch ever is enough to take the top spot. For now.

But, if Manning manages to win the Super Bowl, he’ll move Montana to number two. A good game against one of the greatest pass defenses ever would be the cherry on top of a marvelous season. Manning’s RANY/A was “only” +3.0 this season, but quantity carries the day here. Manning’s Broncos set the record for points scored in a season, while the quarterback broke both the passing yards and passing touchdowns records. So far, Manning has completed 72% of his passes for 630 yards (8.0 Y/A) and 4 touchdowns with one interception in two playoff games. Denver has punted just once in the playoffs.

Manning’s 2013 regular season was brilliant. By adding a Super Bowl trophy, it should be remembered as the greatest quarterback season of all time.