The 26-year-old Northwestern product opened the 2017 campaign in fine fashion. He tossed six touchdowns and ran for a score as Denver scored victories over the Los Angeles Chargers and Dallas Cowboys.
His play faded from there, however, which jump-started a quarterback carousel for the Broncos, who also tried Brock Osweiler and Paxton Lynch.
As a whole, the team's QBs finished the regular season with a combined 73.0 passer rating, which ranked 31st in the NFL ahead of only the winless Cleveland Browns (61.4).
Denver general manager John Elway told reporters during his postseason press conference in January the franchise planned to address the issue:
"We expect to have an answer there, however that goes. I think that thought process makes me think we're going to have a better year. Because the fact is we've got to figure out how to get that position playing better. ... There is no doubt we've got to get better at that position. For us to have a chance to get better, we've got to get better at that position."
Siemian, who finished the season on injured reserve with a shoulder injury, is under contract for one more season under his rookie deal.
He owns a lackluster 79.9 passer rating across 26 career appearances. It's unclear whether the potential trade interest would be from teams that seek a new starter. It's more likely he'd be pursued by front offices that are looking for a backup who's flashed some upside.
Meanwhile, the Broncos could make a play for Kirk Cousins in free agency or use the fifth overall pick in the draft on one of the 2018 class' several high-profile quarterback prospects.