The Jacksonville Jaguars are almost universally considered the NFL's worst team. This weekend, they're playing the Denver Broncos, widely deemed the league's best. So why are the Jags a hot bet?

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Thus far in the 2013 NFL season, the Jacksonville Jaguars are 0-5. The team’s opponents have outscored them by a combined 112 points. The Jags are almost universally considered the NFL’s worst team. So why are so many bettors favoring the Jaguars this weekend, when they’re heading to Denver to play the team widely deemed tops in the league, the undefeated Broncos?

They’re not betting that the Jaguars will actually win the game. That would be perhaps the biggest regular season upset ever. Instead, they’re betting that the Jaguars will cover the spread, which at 28 points is either an all-time high or ties the record for the biggest ever spread in NFL history. (It’s the highest ever since the NFL and AFL merged in 1970, though ESPN researchers turned up a 1966 game when the Baltimore Colts were also favored over the expansion Atlanta Falcons by four touchdowns.)

Even with the record-high spread, is there a chance the game could be “close” enough for the Jags to cover? Absolutely, many say.

While spreads of 30, 40, even 60 points are fairly routine in college football, as a recent Wall Street Journal story pointed out, the NFL has a much more even playing field. Since the AFL-NFL merger 43 years ago, only nine games have ever had a point spread in excess of 20 points, the Las Vegas Sun reported. In eight out those nine cases, the underdog covered.

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The big reason that NFL games are rarely won by more than three touchdowns is that, unlike in the college game where large victory margins factor into rankings, pro teams don’t care how much they win by. Once an NFL team is assured of a victory, there’s a tendency to play it safe and remove top players so they don’t get hurt during “garbage time,” even if doing so allows the opposing team to put some easy points on the board. As Johnny Avello, director of race and sports at the Wynn Las Vegas, told Businessweek, “Pro football players are happy to get out with a W and no injuries.”

It’s this line of thinking that had the majority of the early action favoring Jacksonville this week, even though Peyton Manning and the Broncos have scored the most points through five games in NFL history, and even though the Jaguars have failed to cover previous spreads against teams such as the mediocre Rams (12.5 points) and the much stronger Seahawks (20 points). In fact, after most bets—some of them quite large—earlier this week picked Jacksonville with the 28-point spread, the line offered by many Las Vegas bookmakers shifted from 28 to 27.5, and even 27 points in some instances.

Overall, however, the average gambler doesn’t really know what to make of such a gigantic point spread. Kevin Bradley, sports book manager at Canada-based Bovada.lv, told the Florida Times-Union that a huge spread tends to scare bettors off, and that he didn’t expect to see an especially high level of interest in the Jags-Broncos game. Bradley did predict, however, that starting on Thursday some oddball prop bets would pop up related to the game, such as whether or not Denver quarterback Peyton Manning will be pulled from the game, and whether Denver will cover the spread at any point during the game.

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Bradley also noted that in a totally theoretical matchup of the Jacksonville Jaguars and college’s top-ranked Alabama Crimson Tide, the Jags, though pathetic by NFL standards, would be the favorite. “I would say the spread would be that Jacksonville would be about a 17 ½-point favorite over Alabama or against any top-10 college team,” he said. “There’s still a really big gap between NFL and college.”