DENVER -- Getting a rare start because of an injury to star cornerback Aqib Talib, Bradley Roby wound up as the spearhead in a rugged defensive display by the Dener Broncos.

Roby returned an interception 49 yards for a touchdown and Denver's defense twice turned San Diego away in the waning minutes for a harrowing 27-19 win Sunday over the Chargers.

"When Talib (back injury) said he wasn't playing, I just looked at it as I have to step up and use this opportunity to get better," Roby said.

And Roby and the rest of the Broncos also did it for most of the game without defensive coordinator Wade Phillips, who was carted off the field midway through the second quarter after a Chargers player inadvertently barreled into him after going out of bounds during Roby's interception return.

The game was stopped for several minutes with players on both teams taking a knee and watching medical staff tend to Phillips, who also has coached with the Chargers during a distinguished NFL career.

Phillips was placed on a stretcher and immobilized before being lifted onto the cart and driven off the field. He was taken by ambulance to a hospital.

The Broncos said he was alert and had movement in all of his extremities, and linebackers coach Reggie Herring finished the game up as the Broncos defensive play-caller.

"When Wade went down, it was like, 'Man, what's going on?'" Roby said. "But all signs were saying that he's good and he'll be fine. Reggie, our linebackers coach, was like, 'I got this, I got you.' And we just rallied around him."

And they rallied to the ball.

San Diego's last-gasp drive was stopped near midfield when Philip Rivers, under pressure from the pass rush of the Broncos (6-2), threw incomplete on fourth down with Denver's offense taking the field to run off the last few seconds of the game.

"They're a great defense," Chargers coach Mike McCoy said. "They feed off the turnovers. It starts up front with their front getting after the quarterback. There were some tipped balls in there, things like that. It creates problems for you."

Struggling much of the day, Denver's offense finally clicked with Trevor Siemian leading a 75-yard drive that newly-activated running back Juwan Thompson finished with a 1-yard touchdown plunge with a 12:32 left to play for a 24-13 Broncos' advantage.

"We had a lot of help from the defense, so we found a way to get it done," said Siemian, who completed 20 of 38 passes for 276 yards and an interception. "There were a lot of inconsistencies across the board and I think I have a lot of room to get better. But we found a way to win, which is nice."

San Diego (3-5) wasn't finished. Cornerback Casey Hayward intercepted a pass that skipped off the hands of Jordan Norwood, returning it 24 yards for a touchdown. An offensive interference penalty negated a successful two-point conversion and, when the Chargers tried again, Rivers' pass fell incomplete.

Rivers finished 20 of 47 for 267 yards, two touchdowns and three interceptions while being sacked four times.

"It wasn't my best game by any means," Rivers said. "We didn't play our best. They're to be commended for causing us not to play our best."

Siemian went to work again and completed a 40-yard pass to Demaryius Thomas, leading to Brandon McManus' 22-yard field with 5:19 left and a 27-19 Denver lead.

San Diego fought back to get within a 1st-and goal at the Denver 2, but the Broncos defense held with rookie cornerback Lorenzo Doss knocking Rivers' fourth-down pass into the end zone intended for tight end Hunter Henry away.

That allowed Denver to take over on downs with 2:36 left to play, but the Broncos failed to get a first down, the Chargers used two of their timeouts, and San Diego got the ball back at its 33-yard line with 2:08 left.

The Broncos stretched their lead to 17-7 on Devontae Booker's 3-yard touchdown run with 12:45 remaining in the third quarter and were an outstretched arm away from adding another touchdown by Booker. But as the running back, after catching a short pass, moved the ball from one side to another to go for the goal line pylon, San Diego linebacker Korey Toomer knocked the ball out and linebacker Jatavis Brown fell on it at the 2-yard line.

Rivers, whose second and third interceptions of the day preceded Booker's touchdown and near miss, then led the Chargers on a 98-yard drive that he finished with a 14-yard touchdown pass to wide receiver Travis Benjamin with 4:02 remaining in the third quarter.

Linebacker Shaquil Barrett blew through protection on the ensuing conversion attempt to block the extra point by kicker Josh Lambo, leaving the Chargers behind 17-13.

Unable to get untracked offensively in the first half, the Broncos nevertheless led 10-7 at halftime behind Roby's interception return for a touchdown.

The Chargers had a chance to pull into a tie with 54 seconds left in the second quarter but Lambo's 45-yard field goal attempt sailed wide left.

Roby produced Denver's third defensive touchdown of the season when he corralled a pass that deflected off the hands of wide receiver Tyrell Williams. He took off down the left sideline, outrunning tackle Joe Barksdale and dodging Rivers near the goal line before going into the end zone.

Denver got on the scoreboard first with a 28-yard field goal by Brandon McManus. San Diego answered with a long drive ending in Rivers' 7-yard touchdown pass to tight end Antonio Gates.

NOTES: Philip Rivers and Antonio Gates connected in the first quarter for their 80th touchdown, extending their NFL record for touchdown receptions between a quarterback and a tight end. ... San Diego LB Denzel Perryman left the game in the second quarter with a hamstring injury. ... Denver OLB DeMarcus Ware was active for the first time since breaking his right forearm during a Week 2 game against Indianapolis. ... CB Aqib Talib was among Denver's inactive players after missing practice time during the week because of a back injury. ... San Diego LB Jatavis Brown left the game in the third quarter with a knee injury.