SAN DIEGO -- Mike McCoy's voice cracked, and the San Diego coach couldn't hide his misty eyes. Or the relief that the Chargers didn't blow another lead.
"I am worried about our team," McCoy said, when asked if he feared for his job with another loss. "That is what I do every week."
San Diego (2-4) snapped a three-game overall losing streak and broke a 10-game skid against AFC West teams.
The Broncos (4-2) dropped their second consecutive game as they struggled on offense throughout the game.
Rivers completed 18 of 29 passes for 178 yards and a touchdown. With a short flip to tight end Hunter Henry that turned into a 12-yard completion in the second quarter, Rivers pushed his total to 43,047 yards. He ended the night with 43,094 yards.
Dan Fouts threw for 43,040 yards in his 15-year career, all spent with San Diego from 1973-86.
"This one was definitely special," Rivers said. "I had a poster of him on my wall, and now I'm on a list next to him."
Chargers running back Melvin Gordon had a game-high 94 yards on 27 carries.
"You got to give them credit," Denver interim coach Joe DeCamillis said. "We knew it would be a tough game because they have played a lot of close games and not won."
Broncos quarterback Trevor Siemian, who didn't start Sunday due to an injury to his non-throwing shoulder, was 30 of 50 for 230 yards and a touchdown.
"We didn't make the most of our opportunities, especially early in the game," he said, "but we showed a lot of resilience at the end."
Siemian hit Bennie Fowler for a 5-yard scoring pass midway through the fourth quarter, drawing the Broncos within 21-10.
Denver made another push with four minutes remaining when it appeared running back C.J. Anderson scored. However, the Broncos were flagged for holding, and Chargers linebacker Jatavis Brown, who had a sack in the series, forced a Demaryius Thomas fumble.
Denver got a 46-yard field goal from Brandon McManus with 27 seconds left to make it 21-13, then recovered an onside kick. The Broncos took a final shot from the Chargers 45-yard line, but Siemian's pass was deflected by Dexter McCoil.
"Gosh, you can only imagine how tough it has been with some of the losses we have had," Rivers said. "You get labeled a bad team, and I know some of the mistakes we've made, that is what bad teams do, that is what 1-4 teams do. But we have been so good in so many of those games. So we knew what we were capable of."
The Chargers padded their cushion to 21-3 early in the fourth quarter with a safety after the Broncos were flagged for holding in the end zone.
Denver's Jordan Taylor fumbled after a third-quarter reception, forced and recovered by Korey Toomer. A personal-foul penalty added 15 more yards as the Chargers set up shop at the Broncos 20-yard line. However, San Diego converted the miscue into just three points on Lambo's third field goal, a 31-yarder, for a 16-3 advantage.
Lambo kicked a 21-yard field goal to give the Chargers a 13-3 third-quarter cushion. San Diego was in position to score after Gordon's career-long 48-yard run put the ball on the Denver 6. The Chargers advanced 4 more yards but were denied a touchdown.
Denver pulled within 10-3 in the second quarter, thanks to a bungle by the Chargers.
Travis Benjamin let a punt glance of his leg, and it was recovered by the Broncos at the San Diego 11. However, the Chargers' defense stiffened, surrendering only a McManus 29-yard field goal.
The Chargers struck first with an impressive 12-play, 75-yard drive that was capped by Henry's 5-yard scoring catch. Rivers, spotting his tight end matched against cornerback Chris Harris Jr. in single coverage, fired a strike to Henry despite Harris' presence. After seven minutes, the Chargers were ahead, 7-0.
Lambo's 37-yard field goal with 10 minutes left in the half stretched the Chargers' lead to 10-0. San Diego converted a fourth-and-1 at the Denver 20 on Gordon's 1-yard run, but the Chargers stalled and settled for the field goal.
NOTES: Denver head coach Gary Kubiak didn't attend the game as he deals with migraine headaches. He was replaced by Joe DeCamillis, the special teams coordinator. ... TE Virgil Green (calf) and RT Donald Stephenson (calf) returned to the Broncos' lineup. ... Chargers CB Brandon Flowers (concussion) missed his third consecutive game. ... San Diego backup QB Kellen Clemens is the new holder. ... Chargers minority owner George Pernicano, who died last week, was honored with a pregame moment of silence.