Tom Brady or Bill Belichick: Who contributed more to Pats' dynasty?

— -- There came a point over the past couple of years when Tom Brady began to be described as the greatest of all time. You can even call him the GOAT, although calling someone a "goat" out loud still feels like something you'd need to start apologizing for halfway through. You can certainly make a case that Brady is the best quarterback who has ever lived, or pick Brett Favre, Peyton Manning, Johnny Unitas or one of a handful of other options. Obviously, Brady belongs in the discussion.

His coach also has a strong case for his own honors. Bill Belichick has won seven Super Bowls, including five as head coach of the New England Patriots. A win on Sunday would make him the first person in league history with eight Super Bowl rings. He has pieced together 15 consecutive 10-win seasons in a league in which the previous record was eight. Since 2001, the Patriots have won 209 games, 30 more than any other team. Given the era in which he competes, you wouldn't be wrong to say that Belichick is the greatest head coach of all time.

You can probably see where this is going. It's impossible to directly compare Brady and Belichick, given that they have different jobs and each played a huge role in the other's success. It would be foolish to suggest that Belichick could have accomplished everything he did over the past 17 years without Brady, or vice versa. Unless we live in the alternate dimension in which Belichick passes on Brady to draft Tim Rattay, we'll never get to see if Belichick or Brady could have done it alone.

A question we can ask, though, is this one: Between the two of them, has Belichick or Brady contributed more to the success of this Patriots dynasty? It's impossible to answer definitively, but the questions we ask on the way to finding a solution might be illuminating in themselves. You'll also find at least one fact that might influence your opinion of whether the dominant duo are going to beat the Philadelphia Eagles?to win another Super Bowl.

Let's run through a few questions and see what each tells us in pitting (arguably) the greatest head coach of all time against the greatest quarterback of all time:

1. How has Brady performed without Belichick during his career?

Brady has spent his entire professional career with Belichick as his coach, so we have very little data here. At Michigan, Brady was a successful passer, although his 20-5 record over his final two seasons had some help from a defense that ranked 14th in the country during Brady's junior season. He threw a total of just 618 passes over those two starting campaigns in an offense built around running back Anthony Thomas, who has been out of the NFL for more than a decade.

It's pretty clear the league didn't think much of Brady's success. He had a third-round grade coming out of school and fell to the end of the sixth round, where the Patriots took him with the 199th selection. Things have gone pretty well since.

2. How has Belichick performed without Brady during his career?

The 65-year-old served in various roles for the Colts, Lions, Broncos and Giants between 1975 and 1984, but let's start with 1985. As a defensive coordinator, Belichick was excellent. During his six-year stint as defensive coordinator with the Giants under Bill Parcells, Belichick's defenses finished with an average rank of just over fifth in points allowed and placed seventh or better in each season between 1986 and 1990 by DVOA. (There is not yet DVOA data for the 1985 season.) His defenses helped win two Super Bowls while holding two of the league's best offenses below their season averages.

Belichick later took over a Jets defense that ranked 29th in points allowed and immediately delivered three consecutive top-10 finishes from 1997 to 1999 before famously (and perhaps apocryphally) resigning as "HC of the NYJ" and leaving the Jets to take over with the Patriots. Belichick certainly had an excellent mentor in Parcells, but it's worth noting that Parcells didn't field a single defense that ranked in the top 10 in points allowed without Belichick involved during his time with the Patriots (where Belichick spent 1996 as a defensive backs coach) and just one in four years with the Cowboys.

By all accounts, Belichick was one of the best defensive minds of his generation. His first run as a head coach was far more forgettable. Taking over a 3-13 Browns team, Belichick managed to coax Cleveland to a 6-10 record in Year 1. It was a promising start, but the Browns went 7-9 in each of the next two seasons before finally breaking through with an 11-5 season and a playoff win in 1994. And yes, if you're wondering, Belichick is the last Cleveland Browns?coach to win a playoff game.

One 5-11 season later, though, and Belichick was unemployed. Art Modell fired Belichick as the Browns moved to Baltimore to wild critical acclaim, with Belichick seen as a pariah within the local and national media. Belichick struggled to find a consistent solution at quarterback, finding success only after replacing Bernie Kosar with veteran import Vinny Testaverde. His drafts also were mediocre, with five years of picks delivering just one Pro Bowl player in safety Eric Turner. It's impossible to say Belichick was an effective head coach in Cleveland.

You would imagine Belichick learned from his mistakes during his first time as a head coach, but he didn't enjoy immediate success with the Patriots.?He took over a team that had gone 27-21 under three seasons with Pete Carroll and went 5-11 despite the presence of Drew Bledsoe on the roster. It was only when Bledsoe went down with a sheared blood vessel in his chest two games into the 2001 season that Belichick turned things over to Brady, who took over until the AFC Championship Game. A Brady ankle injury forced Bledsoe back into the game, and Belichick's special teams blocked a field goal and returned it for a critical touchdown before two late Patriots interceptions sealed a 24-17 win.

Since then, Brady has started 273 of New England's ensuing 292 games, missing just 19 regular-season contests. Fifteen of those came during the 2008 season, when Brady tore his ACL during the first half of the season opener. Belichick was forced to turn over things to the unheralded Matt Cassel, and while Cassel was handed the reigns to what had been one of the most devastating offenses in league history, Belichick couldn't coax the same brilliance out of a similarly unheralded backup.

The 2008 Patriots missed the playoffs, although their absence masks what was still a very good team. Those Pats are the only team in the 16-year history of the league's current playoff structure to miss the postseason with an 11-5 record. They finished ninth in overall DVOA and seventh in offensive DVOA despite missing Brady for virtually the entire season, although both marks were down from leading the league the previous season. The defense, coincidentally, was the weak link of the 2008 team. New England finished 17th in defensive DVOA.

Eight years later, the Deflategate scandal led Brady to be suspended for the first four games of the 2016 season. With months to prepare, Belichick and offensive coordinator Josh McDaniels coached up Jimmy Garoppolo, who played six excellent quarters of football before going down with a shoulder injury. The Pats then won a third game with rookie? Jacoby Brissett under center before being shut out by the Bills 16-0 in Week 4.

In all, Belichick has gone 13-6 (.684) in 19 games without Brady at quarterback for the Patriots. To put that in context, no other team?in the league besides Belichick's Patriots has posted a winning percentage higher than .684 since Belichick and Brady joined forces in 2000. Nobody would argue that Belichick doesn't need his Hall of Fame quarterback, but the Patriots have been extremely good even without Brady at the helm.

3. How has Belichick performed after losing members of his staff?

Admirably. During his time with the Patriots, Belichick has changed his offensive and defensive coordinators a combined eight times. When Josh McDaniels and Matt Patricia likely leave this offseason to become head coaches, it will mark the sixth and seventh time a Belichick coordinator has left to become the head coach of an NFL team or a major NCAA program. The only Belichick coordinator to leave the team without becoming a head coach is Dean Pees, who left after his contract expired.

Belichick has yet to fire a coordinator in 16 years on the job. Furthermore, Belichick spent three seasons in this run without an offensive coordinator and three more without a defensive coordinator. It's staggering that Belichick has been so consistently impressive while shedding coaching talent and a testament to his ability to develop young coaches from within. McDaniels joined the staff as a coaching assistant in 2002; Patricia joined two years later.

4. How has Brady performed when the Patriots have moved on from key members of the offense?

Again, it's difficult to give anything but glowing praise here. The Patriots have gone through several offensive iterations during their run with Brady, both in terms of style and personnel. Just three of the 10 offensive starters who lined up alongside Brady against the St. Louis Rams in Super Bowl XXXVI were starting against the Panthers two years later.

Belichick mostly avoided investing in skill-position talent (aside from Corey Dillon) during the early days of the Brady-Belichick era, preferring homegrown players such as Deion Branch and David Givens and ageless veterans such as Troy Brown and Kevin Faulk. The Pats did invest first-round picks in tight ends such as Daniel Graham and Benjamin Watson, but by 2006, Brady was throwing to a 35-year-old Brown and low-budget castoffs such as Reche Caldwell and Doug Gabriel.

Things changed in 2007, when the Patriots blitzed the league with a spread attack built around imports such as Randy Moss, Donte' Stallworth and Wes Welker. The Moss-Welker core lasted four years before Moss was shipped off to Minnesota in 2010, which was also the year the Pats drafted Aaron Hernandez and Rob Gronkowski. The versatile tight ends became the focal point of New England's attack until 2013, when Hernandez was released by the team after being arrested in connection with a homicide.

Welker and fellow veteran Brandon Lloyd left after 2012 and were replaced by the combination of Julian Edelman and Danny Amendola. Edelman and Gronkowski have been the focal points of the offense ever since, along with a bevy of useful running backs and veteran secondary weapons such as? Chris Hogan and Brandon LaFell. Brandin Cooks was acquired this offseason, giving the Pats their most high-profile wideout acquisition since the trade for Moss a decade ago.

Through all of this, Brady has remained remarkably consistent. His numbers improved dramatically during that 2007 season and have stayed at a high level ever since. Brady lost a Hall of Fame wideout (Moss), a hyper-productive slot receiver (Welker) and an athletic freak at tight end (Hernandez) and?he didn't skip a beat.

The one concern you might have as a Pats fan, though, is how Brady hasn't been the same quarterback without Gronkowski in the lineup. Since the Arizona product entered the league in 2010, Brady's drop-off with and without Gronkowski is stark. The 40-year-old has posted a 106.5 passer rating and a 77.9 Total QBR with Gronk on the field but has mustered only a 90.3 passer rating and a 62.1 Total QBR when Gronkowski has been sidelined.

A 90.3 passer rating is still pretty good, but we're looking at the difference between Aaron Rodgers (who has a 105.8 passer rating over that time frame) and Matthew Stafford (90.6). Gronk matters, and the Patriots would be a drastically different team if their star tight end isn't able to recover from a concussion and play Sunday. New England's two lowest-scoring performances of the 2017 season came against the Buccaneers and Dolphins, which were the two games Gronkowski missed.

5. Have the Patriots been more dependent upon their offense or defense during their run of dominance?

This is the critical question. It's too simplistic to assign Brady sole credit for the offense and Belichick full credit for the defense, but you get the idea. Have the Patriots been driven by their offense or their defense? Let's use their rankings by DVOA (which adjusts for game situation and context) from year to year to see where they've been most effective:

You can see how dominant the Patriots' offense has been for what amounts to a 14-year run of success; it hasn't ranked below seventh since 2003 and has 11 top-five finishes over that stretch. You also can see how the defense has struggled to keep up; after an impressive run early during the Belichick-Brady era, the Pats haven't posted a top-10 rank in defensive DVOA in more than a decade and produced the worst defense of the Belichick reign this season.

The correlation between offensive performance and wins (0.52) has been far stronger for the Patriots than defensive performance (-0.29) over this time frame. The average Pats season has seen them finish fifth in offensive DVOA and 16th -- essentially league average -- in defensive DVOA. So, is it fair to say the Patriots have been more dependent upon their offense than their defense?

Not so fast. Let's specifically look at those five seasons in which the Patriots won the Super Bowl -- 2001, 2003, 2004, 2014 and 2016 -- and look at their ranks in DVOA those years:

That's a much more balanced group of teams, owing to a much improved set of Belichick defenses. Their average offensive rank is seventh, and their average defensive rank is 10th. The Patriots defenses that haven't been up to snuff haven't made it to the promised land. Five Patriots defenses have ranked among the bottom half of the league in DVOA. Those teams have gone 4-4 in the postseason and made it to just one Super Bowl. In that game, the 2011 Pats and their 30th-ranked defense fell in an upset loss to the Giants.

There's a sixth defense to add to that list, given that the 2017 Patriots ranked 31st in defensive DVOA. These Patriots have made it to the Super Bowl, and their defense has tightened up after an ugly start to the season. They're favored in Vegas by 4.5 points, and it would hardly be a surprise if a defense facing a backup quarterback did enough to come through and deliver a sixth ring for Brady. If Nick Foles is able to move the ball on a Patriots defense?that?has just one takeaway in its past six games, though, it wouldn't be shocking, either.

So ... Belichick or Brady?

Well, the simple answer is both. It would be impossible to choose between Belichick or Brady, and there's no way the Patriots of the past 17 years would be the Patriots with one or the other in a different city.

The more nuanced answer? Well, Belichick has had a coaching run up there with some of the greats in the history of football, and he?has done it in an era in which it's more difficult to build and sustain success under the salary cap. He could very well go down as the greatest coach in modern American sports. There's not a single team in the league who wouldn't fire its coach to hire Belichick tomorrow.

And yet, there's a reason top-level quarterbacks get paid about twice as much as top-level coaches. Brady has been the cornerstone of an offense that has managed to cover for a decent-or-worse defense over the past decade, even while swapping out key offensive pieces over and over again. He continues to play at a high level after turning 40. Belichick certainly deserves some credit for providing Brady with the infrastructure to succeed, especially early in the future Hall of Famer's career, but who else could have led the Patriots back from down 28-3 in the Super Bowl?

Brady is the best draft pick of all time, arguably the greatest quarterback of all time, and the most important piece of this Patriots dynasty.