The Broncos biggest question mark isn’t at quarterback.

Or even at punter.

No, at least at those two spots, the last 48 hours have provided some clarity.

It’s going to be Trevor Siemian under center Sept. 8 against Carolina. And when the offense stalls (hopefully not often) it’ll be Riley Dixon punting the football. Adios Britton Colquitt, hello Syracuse rook.

You can scream and tweet all you want about Siemian being the starter and the puzzling release of Colquitt, but both those moves are done. The Broncos will go into the rematch against the Panthers with Siemian and Dixon playing important roles.

What isn’t clear yet is a storyline flying under the radar, and it’s concerning.

The Broncos have a problem at tight end.

It’s Virgil Green and then the end of the world.

Not the end of the world as in time stopping, but the end of the world as in we have no idea what’s there. Jeff Heuerman, John Phillips and Henry Krieger-Coble (HKC) represent the edge of the universe. No one can really wrap his mind around where space ends.

Ok, it might be a little dramatic to declare the Broncos tight end situation one of the greatest unknowns of our time, but Broncos fans should care deeply.

Green has been awesome in the preseason and has established himself as the No. 1 tight end. But after that it’s hard to figure out what this team has.

Gary Kubiak’s offense relies heavily on multiple tight ends being productive, and right now it’s unclear who will be the No. 2, or if any of the above guys are even capable.

Offseason acquisition Garrett Graham was placed on injured reserve Tuesday, so he’s no longer an option. It’s down to the looking-like-a-bust Heuerman, the journeyman Phillips, who has just 45 catches in six NFL seasons, and the undrafted HKC out of Iowa.

Going into camp many expected Heuerman to not only be a key member of the offense, but even battle Green for the No. 1 spot. Hell, a lot of folks thought the third-round pick from a year ago was the favorite.

But once again, Heuerman has proven he’s much better at being hurt than anything else, and even Kubiak is sounding frustrated.

Last Wednesday, he had this to say about the former Ohio State tight end’s inability to remain healthy:

“I’m concerned because we’re counting on him a great deal, but more so his ability to stay healthy and stay on the field. Last year he went through the issues; he’s had hamstring issues throughout OTAs. He was on a pretty good roll there, and here we go again … We’re running out of time, but he is doing better.”

Heuerman did return to practice Monday, but Kubiak gave a very revealing answer at his post-practice press conference.

“Jeff [Heuerman] was back to work today. I’ve got to make a decision on that, but he was back to work today,” Kubiak said.

It doesn’t take a rocket scientist to figure out what Kubiak is getting at. He has to make a decision whether Heuerman needs to start the season on PUP, go to injured reserve or (gasp!) cut the guy just 16 months after spending a third-round pick on him.

The fact the Broncos are at “decision” time already with Heuerman is obviously unnerving. He hasn’t come close to living up to expectations.

After that, Phillips probably ‘is what he is’ this far into his NFL career. Averaging nine catches per season won’t get anyone excited; neither will four career touchdowns.

HKC has shown some flashes this summer, but there’s a reason he went undrafted. His college numbers in four years as a Hawkeye are strikingly similar, and just as mediocre, as Phillips’ NFL stats. HKC finished with just 42 catches and four touchdowns in four seasons in Iowa City.

It would be foolish to discount John Elway in this predicament. No. 7 could still pull off a trade or swoop up a tight end off the street (Owen Daniels?) to rectify the situation. But that’s far from a given.

If the Broncos go into the Carolina game with this current group of four tight ends, someone behind Green is going to have to step up. Right now, it’s unclear who that’ll be, or if any of the three options are up to it.

Keep hollering about decisions made at quarterback and punter all you want, right now Denver’s largest question is at tight end – and it’s not even close.