"What happens when you play a good team like this, the little mistakes blow up in a hurry," McCoy said.
Those mistakes started on the Broncos' third play, when Julius Thomas caught a short pass from Manning and turned it into a 74-yard touchdown.
Cornerback Derek Cox, safety Eric Weddle and rookie linebacker Manti Te'o all had a hand in botching the play.
"Derek and Eric both had a chance there to get him out of bounds and we didn't do it. So it was just poor execution from the snap all the way to the finish," McCoy said.
"We didn't tackle," Weddle said. "Linebacker needs to take him to the flat because that's his guy, Derek needs to either make the tackle or turn him back in and I don't need to assume that the tackle's been made. It's very disappointing, especially for myself. I'm not too happy about it. It's actually embarrassing. But I know it'll never happen again."
Weddle said the pass defense had more mental breakdowns than normal.
"It was just communications. It was nothing to do with the Broncos. It was us 11 not communicating," Weddle said.
Te'o said he's "got to have better eyes" and said he wasn't lined up right.
"I've got to know the situations, my responsibilities, and I've got to do a better job of getting my eyes in the right place," Te'o said. "If I would have lined up in the right position in the first place, it might have turned out better than it did."
Cox was benched the next series and got back in the game only because Shareece Wright was injured. Cox was also benched a week earlier during a 30-24 overtime loss at Washington.
The Broncos took a 28-6 lead before the Chargers scored twice. But having to settle for field goals instead of touchdowns early on hurt the Chargers, who lost their second straight game to fall to 4-5.
"Every possession is so important when you play a team with a quarterback like Peyton Manning," said McCoy, who called plays for Manning last year as Denver's offensive coordinator. "You can't have a little mistake because that one third-down conversion you don't get might lead to points one way or the other, whether it's us in the red area or in the middle of the field. Every possession, you've got to value and understand. You've got to finish in the end zone. Or a third down on defense, you've got to come up with something."
McCoy also said some Chargers spent more time listening to Manning's audibles than they did their own team's calls.
"What happens when you play against a team that's no-huddle the way he is, you listen to all the verbiage, the terminology, you listen to all that's going on," McCoy said. "Sometimes, I hate to say, they probably forget to really listen to the communication on our side, also. There were one or two plays where someone said, 'I didn't get the call,' and then they start listening to what he's doing and all this and they kind of space out. And it's like, 'Now hold on a second, how do you not know what the coverage was or what the line stunt was?' or some little thing.
"The big thing I told the team before the game was all 11 on the same page before every play. That's the most important thing."
Also Monday, left tackle King Dunlap was being evaluated for what could be his third concussion in six games. McCoy said Dunlap showed signs of a concussion while on the sideline and that the team erred on the side of caution by taking him out of the game. McCoy said the team is not ruling out a concussion.
The Chargers play at Miami on Sunday.
AP NFL website: www.pro32.ap.org
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