ENGLEWOOD, Colo. (AP) Joe DeCamillis said he felt like a substitute teacher, in which case the Denver Broncos had better brace themselves for the headmaster's return to work Monday.

Gary Kubiak has a mess on his hands when he gets back from his medically mandated sabbatical.

The Broncos (4-2) have lost two games in five days, dropping them out of first place in the AFC West for the first time since Peyton Manning had to use a GPS to get around Denver in September of 2012.

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The Broncos' 21-13 loss at San Diego on Thursday night was a repeat of Denver's 23-16 loss to Atlanta on Sunday night.

They fell behind early and never recovered because of a mixture of conservative calls, costly flags and a defense that showed up late again.

Aside from one flare-up when kicker Brandon McManus booted a touchback on a kickoff instead of burying the Chargers deep, DeCamillis was emotionless on the sideline and nobody picked up the slack.

''I didn't look at it like I was a head coach,'' DeCamillis said Friday. ''I was almost like a substitute teacher. I was trying to help a friend, help a coach and help win a game. I have a new respect for what he goes through and what he goes through in a game and the preparation. I have a new respect for that. After I got through the game, I felt pretty good. I think I can do it.''

The Super Bowl champs have been dogged by slow starts all season, surrendering points on their first defensive series in five of their six games and on their second series in the other one.

This time, they allowed a touchdown drive and then a 10-minute, 18-play field goal drive that gave San Diego a 10-0 lead and had their offense on the sideline for all but 2:22 of the game's first 19+ minutes.

So, why do they keep deferring when they win the coin toss?

''Yeah, that came up,'' DeCamillis said ''... But I still think with our defense I'm going to put our money on them stopping them every time to be honest with you.''

The Broncos gave up a 5-yard TD toss by Philip Rivers to start the game, then kept the Chargers out of the end zone the rest of the night.

That wasn't enough to extend their NFL-record 15-game divisional road winning streak because:

-Their ground game remains stuck in neutral, although Devontae Booker's 46 yards on five carries might force the Broncos to give him more carries than C.J. Anderson, whose biggest runs were negated by holding calls.

-All five of their offensive linemen were whistled for penalties.

-Demaryius Thomas coughed up the football in the closing minutes.

-Emmanuel Sanders was hobbled by a hip injury in the closing minutes.

-Trevor Siemian rushed his Hail Mary and the heave came up well short of the end zone.

Right tackle Donald Stephenson had three flags in his return to the lineup after a three-week absence with a strained left calf and left tackle Russell Okung had two holding penalties, one of which resulted in a safety and the other nullified a touchdown.

DeCamillis said Kubiak still plans to return to work Monday but hasn't revealed any changes he might make to his daily schedule. This is the second time in three years he's missed a game after a health scare. In 2013, he had a mini-stroke while coaching the Houston Texans and was out 10 days.

Kubiak was transported by ambulance to a hospital after Denver's loss to the Falcons on Sunday. He was diagnosed with a complex migraine condition and ordered to take a week off.

On Thursday night, Okung was taken by ambulance to a San Diego hospital after experiencing concussion symptoms. He was released and flew home with the team.

DeCamillis said Okung is in the league's concussion protocol as is wide receiver Cody Latimer.

The Broncos were given three days off and will return to work Monday to try to fix things.

''We've been in this situation before,'' DeCamillis said. ''We have to make sure that our team stays together, which they will. We lost two games (in a row) twice last year and it turned our pretty well. I think our guys have a really good perspective. They're prideful. They want to come back and show they can do a better job, just like the coaches do.''

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AP NFL website: www.pro32.ap.org and AP NFL Twitter feed: www.twitter.com/AP-NFL

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Follow AP Pro Football Writer Arnie Melendrez Stapleton on Twitter: http://twitter.com/arniestapleton .