For much of a chilly Monday night in Kansas City, backup quarterback Brock Osweiler sat on the bench in an oversized coat. The winter jacket kept warm a right arm that would never be used. Next to Osweiler during breaks for the Broncos’ offense was starter Trevor Siemian, who piled up one costly mistake after another in Denver’s 29-19 loss to the Chiefs. Siemian had completed just 5-of-14 passes for 56 yards and two interceptions by halftime — “horrific,” his coach called the throws — while compiling an 8.9 quarterback rating. Still, Osweiler sat. It wasn’t until minutes after Denver’s third consecutive loss, the offense’s turnovers once again the culprit, that Broncos coach Vance Joseph presented the possibility that someone other than Siemian could get a chance to jumpstart the team’s stuck-in-the-mud offense. Might the Broncos be ready to put that right arm of Osweiler to use? A few bleary-eyed hours studying game film early Tuesday morning wasn’t enough time for Joseph to make that decision. But a choice between starting Siemian or Osweiler, in a game that could determine whether the Broncos maintain a fighting chance in the AFC playoff picture, is looming. “Everything is being explored after losing three in a row and having five turnovers (Monday night),” Joseph said Tuesday afternoon. “I think it’s fair to evaluate everything there. With our team working so hard and our team putting in max effort yesterday and not having a chance to win the football game, I think it’s fair to evaluate the quarterback and all positions.” Siemian was arguably the Broncos’ best offensive player during the team’s 2-0 start. But in the 1-4 stretch to follow, the third-year quarterback has thrown three touchdowns and eight interceptions — including a career-high three against the Chiefs. He also lost a costly fumble against the Chargers in a 21-0 loss Oct. 22. Siemian has absorbed 19 sacks in those five games and has a quarterback rating of 67.1.