SAN DIEGO --The Broncos' league-record 15-game road divisional winning streak ended with a thud at Qualcomm Stadium on Thursday night.

With the offense struggling to move the ball for the first three quarters of the game and the defense unable to get off the field early, the Broncos once again fell behind 10-0 and never fully recovered, eventually falling 21-13 at Qualcomm Stadium for their second defeat in five days.

As was the case last week, the defense allowed some lengthy early drives. But it was self-inflicted wounds that helped doom the Broncos -- particulary 12 penalties for 103 yards, the Broncos' most in a single game since last Dec. 20 at Pittsburgh.

"We know it's mistakes and penalties that are killing us," left tackle Russell Okung said. "I had some tonight that I wish I could take back. A lot of things, we're killing ourselves."

Max Garcia was called for a holding infraction that effectively scuttled a drive at the end of the first half.

The most damaging call of the night came with the Broncos down 21-10, but driving at the San Diego 20 with 4:24 remaining. Trevor Siemian found C.J. Anderson, who darted and dodged his way through the Chargers' secondary for what appeared to be a touchdown, but an Okung holding call wiped it from the books.

"In those crunch-time situations, we can't have those penalties," interim head coach Joe DeCamillis said. "It's just something that we don't do, and we've got to get it corrected quickly."

"You definitely can't allow those things to happen," added TE Virgil Green. "We get a touchdown, C.J. scores, penalty. So we've just got to be a little more disciplined."

Two plays later, Demaryius Thomas fumbled, and the Broncos' best chance at a comeback evaporated -- along with their five-season streak.

1. PRESSURE PHILIP RIVERS

The Chargers had enjoyed more success with downfield strikes this season than in recent years, but on Thursday they opted to emphasize bunch formations and plays set up to create open targets underneath and down the seam -- with Hunter Henry and Antonio Gates as the biggest beneficiaries.

Denver did not finally record a sack for a loss of yardage until 6:46 remained in the game, when Shane Ray and Jared Crick poured through the line to sack Rivers for a 12-yard loss that gave the Broncos hope of a comeback that evaporated on the following possession when Demaryius Thomas fumbled.

2. FIND OFFENSIVE BALANCE

Until Devontae Booker broke loose late in the third quarter for runs of 17 and 16 yards in a three-play span, the Broncos' ground game did little to give the offense the balance it needed to find.

Until late in the third quarter, Booker and Anderson combined for just 23 yards on 10 carries, which kept the Broncos from mounting any kind of extended drives to give the defense a rest after it was on the field for 12- and 18-play Chargers series to open the game.

With the offense continuing to struggle, the Chargers were able to slowly pull away, settling for four field goals that gradually stretched their lead to 19-3 by the end of the third quarter.

Booker's runs galvanized the Broncos, and Anderson had a 15-yard run later that series that was called back because of a holding penalty. But with a three-score deficit in the fourth quarter, the threat of the run was effectively gone.

3. WIN THE TURNOVER BATTLE

With two fumbles apiece, this ended even.

All of the Broncos' 10 points were set up by their recoveries of muffed punts -- one of which was a free kick after an end-zone holding penalty gave the Chargers a safety and a 21-3 lead early in the fourth quarter.

Jordan Taylor and Donald Stephenson gave the Chargers their third field goal of the game with a fumble and an unsportsmanlike conduct call, respectively that set San Diego up at the Denver 20. Good open-field defense stopped the Chargers after seven yards on three plays, but that giveaway cost the Broncos three points.

Thomas' fourth-quarter fumble cost the Broncos more -- a chance at a comeback win. Although the offense had been knocked back by a holding penalty -- that wiped an Anderson touchdown off the scoreboard -- and a sack, it was the fumble that provide the final blow that felled the Broncos. They got the football back once more, but the defense had to use all of the team's timeouts to set up that possession.