The euphoria surrounding the Denver Broncos has reached epic heights — they will quite possibly be the biggest favorite in the history of the modern NFL this weekend. While their offense has indeed been a marvel to watch, it is tough not to be concerned about the defense.

Tony Romo has had some very good days in his career, but none have been better than he had last Saturday. He threw for 506 yards, had five touchdowns, and even the interception that ultimately cost him the game wasn’t entirely his mistake as opposed to something the Denver defense forced. His yards per attempt of 14.1 was other-worldly — more than three yards better than Manning has been in any game in this historic season. Romo has quietly had a solid year, but this was far beyond what we have seen from him.

Denver has been very good against the run — they rank first in the league with just 69.6 yards allowed per game, and Dallas had just 52 on the ground. In large part, though, that is because teams have been able to pass against them so effectively. They are dead last in the NFL with 347 passing yards allowed per game. That is somewhat inflated by Romo’s big day, but even beyond that this has been an issue. Two Philadelphia passers combined for 9.2 yards per attempt. Oakland’s Pryor and Flynn, with a TD pass from Darren McFadden thrown in for good measure, averaged 9.5. Eli Manning, who has been lousy this year, averaged 7.2. Anything over seven yards per attempt is a sign of a good all-round passing day for an offense, so Denver is definitely vulnerable through the air, and it has only gotten worse with each outing.

What does the defense mean for Denver and, more importantly, for handicapping them going forward? Here are five issues to consider:

Remember the hashmarks: The most shocking thing about the Denver defense through these early games has been how predictable the vulnerabilities have been. Most notably, there is a lack of communication between the safeties and linebackers that has consistently left them vulnerable on the hashmarks. Terrance Williams torched that hole for an 82-yard touchdown, and Romo consistently made the Broncos pay there using his tight ends. The Broncos were horrible at defending the tight end in the hashmarks last season, and while it looked like there was some progress being made early, those issues have again come to the forefront. The Chargers, Colts and Chiefs are all coming up on the schedule, and they all use their tight ends very effectively. The ability of the Broncos to adjust and improve here will have a lot to do with their success this season — especially when it comes to covering spreads.

Miller will help create pressure. Maybe: Von Miller has reached the last game of his six-game suspension, so he should be in the lineup for the game against the Colts. In the Dallas game it was at times shocking how much time Romo had in the pocket. It was seemingly endless, and Romo took advantage. Miller’s return will help that significantly because he can create more pressure and put offenses on edge. Maybe. As good as he is, it’s hard to know for sure what we will see from him in the short term. He hasn’t been practicing with the team or working with coaches outside of the strength coaches, so it’s hard to know how much rust there will be and whether he will be comfortable and productive in the defensive system right away — and physically ready to play a lot. He has had a tumultuous offseason as well, so we can’t be sure until he plays that he will be mentally checked-in and committed. We also can’t be sure what substances won’t be flowing through his veins that were before and what impact that will have. Miller’s impact could be significant, but it would be a real mistake to view him as a savior without evidence.

Jacksonville could mask issues: The Jaguars are a historically lousy team. Just irredeemably bad. Jacksonville may be able to score a few points late if Denver opens up a big early lead and lets off the gas, but it is hard to believe that they will move the ball very well at all early on. The season is short enough that a good performance against the Jags could improve the stats significantly in some problem areas. The passing yards per game will likely be quite a bit better, for example. It will be important for bettors to not let what happens on Sunday have any real impact on how they view this team defensively — unless, of course, the Jaguars are able to have a big offensive day.

Luck looms: The Broncos play the Colts in two weeks. Luck has matured and is playing well — especially late in games. He’ll be able to test this defense. So will Philip Rivers after the bye week, and Robert Griffin III could as well if he is more capable after his bye week than he has been up to this point. That’s three tough QB tests in the next four weeks — and that’s before two games against Alex Smith that sandwich a trip to play Tom Brady. That’s a lot of challenging QB tests in coming weeks — and tests of different styles. Things don’t get easier for this defense after this week.

The public won’t care: The public will not put a second of consideration into the defense when betting on this team. They are absolutely in love with this offense and the stories that go with it, and they will enthusiastically back them until they show vulnerability. Sharp money has drawn the historically large spread down slightly against the Jaguars this week, but a strong majority of public bets have still come in on the Broncos. If the defensive issues don’t improve, the team could struggle to cover the spreads that are inflated by the public. Already they are just 3-1-1 ATS — profitable, but not as much as it should be given how dominant they have been.

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