To name a few: An offensive line that can't absorb any more injuries; a defense that needed more than Von Miller's return to repair its problems; turnovers; penalties; play calling.
"You're concerned with all of it," coach John Fox said.
His biggest concerns were the penalties and turnovers. The Broncos (6-1) got flagged for 103 yards; defensive lineman Kevin Vickerson uncharacteristically lost his cool and hit the trifecta one flag each for unsportsmanlike conduct, unnecessary roughness and roughing the passer. The Broncos were a minus-2 in turnovers, and that didn't include the blindside sack on Manning by Robert Mathis that resulted in a fumble and a safety.
"We need guys to grow up and play the way they need to," receiver Wes Welker said Sunday night after the game. "I have no doubt we are going to do that."
The offensive line got pushed around all night. Mathis added two sacks to his total to give him a league-leading 11½. Denver's newest starter is Chris Kuper, who took Louis Vasquez's spot at right guard, while Vasquez moved over to tackle to replace injured Orlando Franklin. Left tackle Chris Clark, the permanent replacement for injured Ryan Clady, was overmatched by Mathis.
Manning got sacked four times and hit 10, which left him looking as skittish as he has in the pocket since he arrived in Denver. Fox wrote off the line's lackluster play to the circumstances of the game.
"I think when you get into a chuck-and-duck kind of game when you're one-dimensional, especially on the road with the crowd noise and against maybe the best pass rusher in football, it doesn't go real well when you're down 19 points or 16 points," Fox said.
Though the Broncos allowed 39 points, Fox actually said he saw "makings of a championship defense" during the second half. Indeed, Denver allowed Andrew Luck only 228 yards passing and the Indy offense played on a short field most of the night. Still, the Broncos walked out of the game in the same place they were when they came in ranked last in the league in pass defense.
Denver has given up 39-plus points twice in the last three weeks. The 28.1 points per game the Broncos allow are more than all but five teams, two of which have faced Denver's high-scoring offense.
Miller's return was uneventful. He finished with two tackles, one for a loss, and two quarterback pressures.
On the turnover front, one of Denver's lost fumbles came from one of the team's most slippery-handed players Trindon Holliday while the other came from Ronnie Hillman, who is built more like a third-down back, but found himself with the ball in a critical goal-line situation.
Asked if there's anything else he can say to Holliday, who has fumbled six times in 18 games with Denver, while also scoring on six kick returns, Fox replied: "Maybe say it differently. He understands that. … We've got to find a way to come up with the ball and hand it to the official."
Fox has been taking heat around Denver for the decision to hand the ball to Hillman on first-and-goal from the 2 with 3:15 left and the Broncos trying to cut into a 39-30 deficit. Hillman lost a fumble and the game was essentially over at that point. Hillman has fumbled three times and lost two over his year-plus career.
"If you follow the game and look around the league, most of your top backs have two or three fumbles," Fox said. "It's not anything we like, not anything we're happy about. ''
While Manning said he was looking forward to the possibility of playing the Colts again, "because that would mean we made the playoffs," Fox refused to be baited into a conversation about how Denver's first loss affects its Super Bowl chances. But his answer suggested he's aware of the standings. The Broncos are a game behind the Chiefs with two games to play against them.
"We're 6-1, not even halfway through the race yet," he said. "We're in charge of our own destiny. Time will tell."
AFC West standings
Team W L T Pct PF PA
Kansas City 7 0 0 1.000 169 81
Denver 6 1 0 .857 298 197
San Diego 4 3 0 .571 168 144
Oakland 2 4 0 .333 105 132