The Denver Broncos ended the season with a 23-9 loss to the Los Angeles Chargers on Sunday to finish 6-10. Here's a recap of the season and what's next:

Season grade: Below average. The Broncos had a pile of injuries, with seven starters, including two Pro Bowl selections in Chris Harris Jr. and Emmanuel Sanders, and 11 players, overall, on injured reserve. They also traded wide receiver Demaryius Thomas to the Houston Texans midseason, had a propensity to get flagged for penalties at the worst times and a schedule that included eight games against playoff teams. Add it all up and things simply did not turn out as the Broncos had hoped. They believed they were a playoff team out of training camp, but were not by the time Christmas rolled around.

Season in review: Since Peyton Manning retired, the team has started four different quarterbacks and has had three consecutive playoff misses. Case Keenum signed a two-year deal in March as the Broncos bypassed a chance at Kirk Cousins, among others, saying Keenum was the best fit in free agency. It was a prove-it contract for Keenum and gives Denver flexibility. The Broncos elected not to use a 2018 draft pick on a quarterback -- they took Bradley Chubb at No. 5 after Baker Mayfield and Sam Darnold were off the board -- and have been scouting the best quarterbacks in the 2019 draft. Keenum had moments when he looked like a long-term solution, but he also had a bumpy road as the Broncos seemed to struggle with their offensive identity. Beyond the close losses, injuries and everything else that happened, they exit the season with a decision to be made at the game’s most important position.

He said it: "Just eliminate the dumb mental errors that we've had. The dumb -- not executing the plays. We know this week we've got to double-team and we have to execute a double-team. We've got to execute it. We have to let all of the little kid stuff, the little kid mess-ups that we've had -- I call them 'high school mess-ups.' The little high school mess-ups, we've got to throw those in the bag." -- Cornerback Harris Jr.

Offseason questions

What happens with coach Vance Joseph? When the Broncos traded Thomas to the Texans, it's difficult to believe the decision-makers, most notably John Elway, thought the Broncos, then 3-5, were a playoff team. In Week 16, Thomas was the second-leading receiver on the team with 36 receptions. So to fire Joseph because the team didn't make the playoffs after slogging through a difficult schedule would raise some questions. If the Broncos do fire Joseph, he would also be the third head coach in the past four who was on the job in Denver for two or fewer seasons; the fourth, John Fox, was fired after a playoff stumble despite four consecutive AFC West titles. The list of potential coaching candidates is not considered strong, so the Broncos have decisions to make about how much of their failings are personnel and how much are coaching.

Is Keenum the answer? Keenum is 30, having completed his first season as a team's unquestioned starter. At his best, Keenum played well in late-game moments when the Broncos needed it, but he also wrestled with turnovers -- Denver was 3-6 over its first 14 games when he threw an interception. He is signed through the 2019 season and the Broncos have no real succession plan. None of the quarterbacks Elway has drafted are on the roster, so what the Broncos want to do with Keenum next season and beyond matters with regard to what they do early in the 2019 draft.

Can the Broncos repeat their work of the 2018 draft? As the Broncos came down the season's stretch, they had 13 rookies on the roster, including eight picks from the 2018 draft to go with undrafted running back Phillip Lindsay, who became the team's leading rusher. They pulled that group together by concentrating on players with proven college résumés, multiyear starters who were leaders or captains. The payoff was a rookie class that was at the heart of the team's success and offered some optimism. The Broncos need a repeat in the coming spring to snap themselves out of the playoff drought.