The great Belichick-Brady betting debate: Who is more valuable?

Why the numbers suggest Brady might have a clear advantage over Belichick (1:56)

Mike Greenberg dives into the numbers behind the most commonly asked question of who is more responsible for the Patriots' historic run, Tom Brady or Bill Belichick. (1:56)

Twenty-to-one. Those were the New England Patriots' odds to win the Super Bowl entering last season's playoffs. They were the longest Super Bowl odds the Patriots had faced in a decade.

Flash-forward three months: Tom Brady is in Tampa Bay, while Bill Belichick remains in New England with an uncertain quarterback situation and an uninspiring roster. Yet, guess what the Patriots' current odds are to win next year's Super Bowl? That's right -- 20-to-1.

Twenty-to-one with Brady, 20-to-1 without him -- that's the power of Belichick in the betting market.

"If this were any other team, we'd probably just adjust them up to 100-1," said Matt Metcalf, sportsbook director for Las Vegas bookmaker Circa Sports. "But with Belichick, you can't do that."

Together, Brady and Belichick spearheaded a dynasty so prolific that not even Vegas could get a grasp on just how great they really were. For 19 seasons, the Patriots covered the point spread in nearly 60% of the games Brady started (and Belichick coached), a remarkable feat that few teams have accomplished.

Bookmakers, despite their best efforts to post odds dissuading bettors from backing New England, ended up rooting against the Patriots weekly. So, in some ways, oddsmakers are saying good riddance to the Brady-Belichick juggernaut. However, they're now faced with another challenge: How do you figure out how valuable Brady or Belichick is without the other?

Why Tampa Bay and New England have similar Super Bowl odds

Twenty-two-to-one. Those are the Tampa Bay Buccaneers' new and improved odds to win the Super Bowl at Caesars Sportsbook. It's a significant move from 50-1, where they stood before the possibility of landing Brady began heating up. The Bucs now have the GOAT at quarterback, yet their Super Bowl odds are around the same or worse than New England's. What gives?

Even at 42, Brady is considered an upgrade over the Bucs' former quarterback, Jameis Winston.

"Brady's got to be worth a few points just in terms of the interceptions he doesn't throw," Caesars Sportsbook director of trading Jeff Davis said.

In addition, Brady will have better weapons at his disposal in Tampa in explosive wideouts Mike Evans and Chris Godwin. Last season, Evans and Godwin each scored more touchdowns and had more receiving yards than the Patriots' leading receiver, Julian Edelman. So why do the Bucs have similar Super Bowl odds to the Patriots?

"It's hard to say," Davis said. "But is there anyone who's done more with less than Belichick? I'd say, no."

While Belichick has the respect of every oddsmaker, there are additional factors keeping the Patriots' odds shorter than a team with a similar roster normally would have.

• New England could sign one of the high-profile QBs on the market, maybe a Cam Newton, Winston or Andy Dalton.

Kenny White, a longtime Nevada oddsmaker who consults for domestic and international sportsbooks, said he views the drop-off from Brady to second-year pro Jarrett Stidham, the Patriots' potential starter, to be 5.5 points. "If the Patriots were to pick up Jameis Winston ... the drop-off is just one point," White told ESPN.

• As long as the Patriots are in the AFC East -- where they get two shots each at the downtrodden Miami Dolphins and New York Jets -- Belichick will seemingly have them in the hunt a playoff spot routinely.

New England is currently the favorite to win the AFC East, listed ahead of the improving Buffalo Bills at even money at Caesars Sportsbook.

"Do I think the Bills are better on paper than the Patriots? Yes," Davis said. "But the Patriots are still the favorites in the division because of the Belichick regime and his ability."

If Stidham is New England's starter, the Patriots' Super Bowl odds will drift back a bit, but maybe not as drastically as some might expect.

"From the bookmaker's perspective," said Las Vegas oddsmaker Dave Sharapan, "you don't have to give 30-1 if they're going to take 20-1."

GOAT of covering spreads

Coaches are measured by championships and straight-up wins and losses. Over the long term, however, coaches' records against the point spread (ATS) can reflect whether their teams exceed or fail to meet the betting market's expectations.

Most coaches who last several seasons end up with an ATS record of about 50%. The elite coaches, though, often are 55% or better. For example, former San Francisco 49ers coach, the late Bill Walsh, covered the spread in 58.1% of his career games.

"For me, it's not even close. Walsh and [Joe] Montana were the bane of my existence," Chris Andrews, sportsbook director at South Point, said. "I always said that I don't hate Brady and Belichick nearly as bad as I should, because I got them right in some big games."

In the Super Bowl era, no coach has covered the spread in more games than Belichick, and his career ATS record of 249-184-10 (57.5%) ranks among the best ever -- but only with Brady. With Brady starting, Belichick is 189-128-7 against the spread (59.6%); without Brady, including his three seasons in Cleveland, Belichick is just 60-56-3 ATS (51.7%).

After taking over for Drew Bledsoe as the Patriots starting quarterback in Week 3 of 2001 season, Brady would miss only 19 games during his career with New England (15 in 2008 due to injury and four in 2016 for a suspension). The Patriots, like most teams missing their starting quarterback, were a different team without him -- even with Belichick as the coach.

According to ESPN's Football Power Index, the Patriots' win probability decreased on average 12.7% in games Brady didn't start. The three quarterbacks who started in place of Brady -- Jimmy Garoppolo, Jacoby Brissett and Matt Cassel -- had a combined average QBR of 65.0. Brady's career QBR is 72.8.

The Patriots went 13-6 straight up and 10-9 ATS in games Brady missed. New England was favored by an average of 5.8 points in Brady starts compared to 2.7 points in games he missed.

Who is more valuable?

Oddsmakers take different approaches to determining the value of a coach, and it's often more art than science.

"It's hard to put a number on it," Davis of Caesars Sportsbook said. "But if I were to power-rank coaches as to what they're worth to the number, [Belichick] is definitely No. 1."

When creating his NFL odds, White gives each individual player a power rating. He factors in coaching by rounding the players' power ratings up for quality coaches and down for subpar ones. It's not a precise metric, but White believes it reflects whether a coach typically gets the most out of players.

"My guestimate is that I rate the Patriots 3.5 to 5.5 points higher because of [Belichick]," White said of his team power rankings.

That's over an entire season, though. In a single game, Brady is more valuable than Belichick to the point spread.

If Brady were to be ruled out suddenly, the point spread on the upcoming game would shift significantly, certainly more than if Belichick were to miss a game for whatever reason. White said he would take a game-by-game approach to any scenario in which Belichick would be out, but would start with only a "one-point deduction, because teams will rally around the absence of a coach for a game or two."

With the draft still to come and a few key free agents still available, White has not done his player power ratings yet, but he says he has a feel for where teams stand as of now.

"With looking at a few changes in the Bucs' roster, including the addition of Brady, I have them one point better than the average NFL team," White said. "The Patriots' power rating without Brady is currently 1.5 points better than the average NFL team."

So which GOAT is more valuable in the betting market's eyes? For one game, Brady unquestionably has more influence on the betting market than Belichick does. For the season, though -- well, the Patriots' odds seem to tell a different story. Now, it's bettors' turn to decide.

The Buccaneers' season-win total has been set at 9. The Patriots' win total? It's also at 9.

ESPN Stats and Information researcher Ryan Satsky also contributed to this piece.