The defense is their Achilles' heel. Peyton Manning came up short in another cold-weather game.
What this loss did was ensure that Denver will need to win at Houston and Oakland in the final two weeks. They can't afford to let off the gas pedal or rest key players down the stretch.
The Patriots can gain control of the No. 1 seed by knocking off the Dolphins in Miami this weekend. They also lost arguably the NFL's most valuable non-quarterback (Rob Gronkowski) in the same game in which they surrendered nearly 500 yards to Jason Campbell's Browns. They are a more flawed team than Denver -- as are the Bengals, Chiefs and Colts.
The Broncos' defense must get their key players back to full strength. Manning must play more like he did in Weeks 13 and 14 than Weeks 12 and 15. But no AFC team has a better chance playing in Met Life Stadium on February 2.
Here's what else we learned in Thursday's game:
1. The race for the AFC's No. 6 seed just got a lot more interesting. The Chargers are now just a half-game behind the Dolphins and Ravens. Whereas Baltimore closes out the season at Detroit, home to the Patriots and at Cincinnati, the Chargers and Dolphins have an easier slate. Among those three wild-card contenders, San Diego's offense is the best unit.
2. There has been no bigger contrast between any NFL player and his pre-2013 reputation than Ryan Mathews, who was branded as a "soft" running back entering the season. Mathews has been a hammer between the tackles, tying Adrian Peterson and LeSean McCoy for the most 100-yard rushing games in 2013. Mathews' 58 carries over the past two weeks are a dozen more than any two-game stretch in his career. A free agent after the 2014 season, Mathews might have earned himself a contract extension with his performance against the Broncos.
3. Keenan Allen is a playmaker. Four of his last five catches have gone for touchdowns. Philip Rivers' go-to guy bolstered his already strong case for Offensive Rookie of the Year with a pair of scores, including a "leaping from the free-throw line" highlight play.
4. A Bolts defense that has been dead last in Football Outsiders' metrics for a good portion of the season has shown backbone the past three weeks, allowing an average of 17 points to the Bengals, Giants and Broncos. Coordinator John Pagano did a commendable job of dialing up blitzes against Manning, and defensive end Corey Liuget made a huge play to force a game-saving interception late in the fourth quarter.
5. Andre Caldwell did an admirable job filling in for Wes Welker, leading the Broncos with 10 targets, six receptions, 59 yards and a pair of touchdowns. Manning still seemed to miss Welker, however, as the offense had three three-and-outs and a four-and-out over a four-possession stretch as the Chargers took control of the game.
6. Manning has thrown 14 touchdowns versus four interceptions in five cold-weather games with the Broncos. His "struggles" in the cold the past two years remain more narrative than reality. With four more touchdowns over the final two games, he will break Tom Brady's single-season record.