Joe Mahoney/Associated Press

The Denver Broncos continue to suffer from a quarterback problem, and the hubris that lingers from the aberration that was their magical 2015 season continues to beset the organization.

Two years ago, the Broncos won Super Bowl 50 in spite of their quarterbacks. Peyton Manning was tired and Brock Osweiler was a deer in headlights, but a superb defense allowed the Broncos to become an enormous 21st-century anomaly.

In the most pass-happy era in NFL history, Denver had the lowest team passer rating in its conference and still won a championship.

Lightning did not strike twice in 2016, when the Broncos still had arguably the best defense in football—they ranked first in terms of DVOA, according to Football Outsiders—but couldn't even get back to the playoffs with 2015 seventh-round pick Trevor Siemian running the show behind center. A game manager at best, Siemian completed less than 60 percent of his passes, averaged just 7.0 yards per attempt and ranked near the bottom of the league with an 84.6 passer rating.

But general manager John Elway doubled down in 2017. He opted against bringing in a veteran at that position, sticking with Siemian and raw second-year first-round pick Paxton Lynch.

Siemian won a camp battle by default (not a particularly good sign) and had a few nice moments early in the regular season. Two weeks in, the Broncos were 2-0 and the Northwestern product had six touchdowns, two interceptions and a 106.9 passer rating. But there was little evidence a quarterback with seemingly clear limitations could sustain that success.

Sure enough, both Siemian and the Broncos have regressed.

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The Broncos have scored just three touchdowns in their last three games, covering a four-week stretch in which they've won just once.

It was one thing to lose 26-16 in Buffalo. The Bills have been defensively stout this season, and everybody suffers from a dud once in a while.

You could even look past another 16-point performance the next week against the Oakland Raiders, because they still managed to win the game in a turnover-free effort.

But what happened Sunday night against the New York Giants confirms this Denver team has severe issues, starting with the quarterback position.

Contenders don't lose 23-10 to previously winless opponents, especially if they're at home and coming off a bye week while that previously winless opponent is missing its top three receivers and two of its best defenders.

Coming off two weeks' rest, the Broncos were embarrassed by one of the NFL's most downtrodden teams in prime time at Mile High Stadium. Much of that falls on Siemian, who threw two first-half interceptions, took four sacks, completed just 29 of 50 passes and was just 5-of-13 with two picks on third down.

Ever since that hot two-game start, Siemian has completed 59.5 percent of his passes for 7.0 yards per attempt. Those rate-based numbers are identical to his 2016 totals. He has two touchdowns to four interceptions and a 72.3 passer rating in that span. Only two qualified quarterbacks—Joe Flacco of the Baltimore Ravens and DeShone Kizer of the Cleveland Browns—entered Week 6 with ratings below that mark.

Siemian is on pace to throw 19 interceptions and take 54 sacks this season, nearly doubling his totals from 2016 in those categories.

Trevor Siemian: 2016 vs. 2017 Category 2016 2017 Completion % 59.5 61.4 TD-INT 18-10 8-6 Yards/attempt 7.0 7.2 Passer rating 84.6 84.1 Sacks/game 2.2 3.4 NFL.com/Pro Football Reference

Siemian is who we thought he was as a seventh-round pick, a tablet-holding rookie and a mediocre sophomore. It still isn't evident he can make big throws to tight spots, especially in key moments. While his decision-making isn't bad for an inexperienced 25-year-old and his footwork is a strength, those attributes aren't enough to make up for his inability to consistently deliver on third down and in the red zone, where he completed just three of nine passes against the Giants. His ball placement, pocket awareness and process time on secondary reads all leave much to be desired as well.

Siemian is likely better suited as a second-stringer rather than a starter. But the Broncos are putting all of their eggs in his basket, perhaps because they believe they can create just enough magic on defense to conjure a repeat of 2015.

That defense hasn't stopped being good. It entered Sunday ranked No. 1 in football. And Siemian has been getting more help this year from his running game, which has received a shot in the arm from veteran Jamaal Charles and the return of C.J. Anderson.

But none of that is enough. Not in this era. Peyton Manning, Tom Brady, Ben Roethlisberger, Eli Manning, Drew Brees and Aaron Rodgers have won 12 of the last 14 Super Bowls. The Broncos bucked a hell of a trend when they won it all despite poor quarterback play in 2015, but it was silly of them to believe they could recapture that without upgrading at the most important position in the sport.

Siemian isn't good enough, and in a conference with the New England Patriots and a division with the Raiders and Kansas City Chiefs, neither are the Broncos.

Brad Gagnon has covered the NFL for Bleacher Report since 2012.

Follow @Brad_Gagnon