The Broncos are pedaling as fast as they can. But it’s hard to get down the road to the Super Bowl when every time the offense takes off the training wheels, quarterback Trevor Siemian falls down and goes boom.

The clock is ticking toward the NFL trade deadline, which expires at 2 p.m. Tuesday. The Broncos are open for business, according to general manager John Elway. Unless Elway can trade for a quality offensive lineman such as Joe Staley of San Francisco or Joe Thomas of Cleveland, the real question isn’t if this Denver season will end in disappointment, but when Siemian will get flattened like a pancake so hard it will require a spatula to peel him off the turf.

Denver beat San Diego 27-19 Sunday. At the mid-way point of the season, the Broncos are 6-2. But you are not always what your record says you are. This is a first-place team with no margin for defensive error.

What left the most lasting impression from this victory was not a brilliant defensive stand that turned quarterback Philip Rivers and the Chargers away from the end zone late in the fourth quarter. It was the frustration in coach Gary Kubiak’s voice when he talked about his team’s offensive woes.

I asked Kubiak his impression of his rushing attack, which gained 57 yards on 25 carries against San Diego.

“It was nonexistent,” replied Kubiak, sounding as if the next teaching moment at practice will be rated PG-13 for language and violence.

Everybody likes Siemian. He walked into his news conference wearing a wrinkled flannel shirt and jeans, looking like a quarterback who sleeps in his mother’s basement. “Hey, Trev,” said linebacker Von Miller, wondering if Siemian was going as a nerd for Halloween. “You got your Peter Parker costume on?”

Yes, Siemian is learning on the job. But by any statistical measure, he ranks in the bottom third of NFL quarterbacks. He fumbled and threw an interception against the Chargers. “I know he got hit way too much and I have to go see why,” Kubiak said.

Siemian needs help. Yes, the acquisition of left tackle Russell Okung on a team-friendly contract in the offseason was savvy shopping by Elway. It also was a necessary act of survival for an offense that sometimes has trouble getting out of its own way in the red zone.

In Kubiak’s scheme, if the Broncos cannot run the football effectively, the coach might as well put his laminated play sheet in the shredder. And unless you’re seeing double after being over-served with orange Kool-Aid, it’s obvious to see Denver is barely half functional along the offensive line.

Elway has tried to broker deals through San Francisco and Cleveland in the past year. He sought a way to take quarterback Colin Kaepernick off the 49ers’ hands, but ultimately failed to see how the dollars made sense. He flushed a deal for Thomas after the Browns kept raising the trade price during the final hours before the deadline in 2015.

A second-round draft choice seems to be fair compensation for either Joe Staley, a five-time Pro Bowler with the Niners, or Thomas, a nine-time Pro Bowler with the Browns. With Cleveland stubbornly clinging to the idea that Thomas is harder to move than Lake Erie, then perhaps Staley is a more reasonable target. The addition of Staley could allow Denver to shift current right tackle Donald Stephenson to guard, where the Broncos are sketchy at best.

Why must Elway explore a trade for an offensive lineman? The true need to do so fell on my head like a ton of bricks in the fourth quarter, with Denver leading 24-19.

Let’s rewind the videotape. Try not to cover your eyes. The Broncos faced second down, a scant two yards from the end zone for a touchdown that would have put away San Diego. Siemian took the snap and handed the football to Devontae Booker for a run off right tackle. It was ugly. Booker went backwards because there was no other way to go with a ton of Chargers falling on him. The drive stalled. Denver had to settle for a field goal and endure another finish of stomach-churning tension.

This offense is enough to give Kubiak a headache.

“We have to find a way to find some consistency,” Kubiak said. “We’re young in the backfield. The quarterback, fullback and halfback: They’re all first-year players. It is what it is. We have to find a way to be consistent with that group.”

Maybe a place to start would be to bring in some veteran muscle on the offensive line.

Unless the Broncos make a deal, I’m afraid the road to the Super Bowl is doomed to end in a brick wall.