ENGLEWOOD, Colo. — Phillip Lindsay's 55-yard run touchdown began a scoring onslaught against the Chargers on Sunday, as the big play started a 28-point second half for the Broncos' offense.

In the wake of Denver's 21-point comeback — the team's largest since a 24-point comeback against the Chargers in 2012 — Lindsay's run was heralded as the turning point.

Head Coach Vic Fangio said Monday, though, that he believes the Broncos' offense began to click two plays earlier. On third-and-8, Drew Lock stood in the pocked and delivered an 18-yard pass to DaeSean Hamilton. The conversion was just the Broncos' third first down of the game, and it kick-started a stretch in which the Broncos scored touchdowns on four of their final five possessions.

"We were struggling as an entire offense in that game obviously," Fangio said. "When you're going three-and-out as many times as we were, your opportunities are not going to be good. You don't have a lot of plays and it's not going to look good. I thought one of the key plays in the game was the third-and-8 conversion prior to Phillip's touchdown run to DaeSean. I think that's the play that got us going. It was third-and-8, if we don't convert that and we punt, then the whole tone of this conversation today would probably be different. It just takes one play. That was a big, big play and we had a big run there by Phillip and all of a sudden, we're back in the game. We still got a lot of work to do, but there's some light at the end of the tunnel."

Asked if Lock and the Broncos can build off Sunday's fourth quarter, Fangio pointed specifically to their third-down performance. After beginning the game 1-for-8 on third down, the Broncos finished 4-of-5 on the crucial down, beginning with the completion to Hamilton.

On the Broncos' final drive, Melvin Gordon III converted a pair of third downs and Denver also twice picked up a new set of downs via pass interference calls.

Entering Sunday's game, the Broncos ranked 29th in the NFL in third-down conversions, with a success rate of just 35.9 percent. Against the Chargers, Denver just slightly improved that number for the game but succeeded at a strong 66 percent clip in the second half.

"I think that's been a big problem for us," Fangio said. "We got that solved in the last quarter and a half yesterday. I don't know that it's solved permanently, but it's a big part of what's been holding us back."

STANDING BEHIND LOCK

Lock struggled for the better part of three quarters on Sunday, as he began the game 10-of-21 for 76 yards, an interception and a 37.0 passer rating.

Fangio, though, said it was "never in consideration" to bench Lock in favor of Brett Rypien.

"The thought didn't cross my mind," Fangio said.

Lock rewarded Fangio's patience, as he completed 14-of-18 passes for 155 yards, three touchdowns, no interceptions, no sacks and a 142.1 quarterback rating in the fourth quarter.

In the process, he became the first Broncos quarterback to throw three fourth-quarter touchdowns since Peyton Manning did so in 2013.

A CAREER BEST

Immediately after Lock threw his interception, Bryce Callahan bailed the Broncos out as he intercepted Justin Herbert on a third-down pass into the end zone.

Matched up against Mike Williams, who has a seven-inch height advantage over the Broncos cornerback, Callahan first ensured the pass wouldn't be completed and then secured the game-changing interception with one hand.

Even an incompletion likely would've sealed the Broncos' fate. The Chargers were within field-goal range, and a 17-point lead may have been insurmountable. Callahan held the Chargers to nothing, though, and the Broncos outscored the Chargers 21-6 over the final minutes of the game.

Fangio, who worked with Callahan in Chicago before the two were reunited in Denver, has been impressed with the veteran's play.

"His quality of play has been really, really good, and we move him around," Fangio said. "When [A.J.] Bouye got hurt, we took him out of the nickel position and left him at corner. He had to move from right corner to left corner. He plays the nickel for us when we can. He's back there catching punts for us. I told him last night and again today that his interception was probably the best play in his career, and I've seen every play in his career. I'm not surprised by it. I've been with him his entire career. He was injured last year. He had a bent screw in his foot that kept him out. I've never had a screw in my foot, but if it's bent, I don't think it's very comfortable. I know everybody was disappointed that we brought him in last year and he couldn't play, but he was injured. I knew how he could play if he stayed healthy, and he's proving that this year."

SHORING UP THE RUN 

Somewhat lost in the Broncos' win was that they gave up a season-high 210 rushing yards, which was the highest allowed total since the team's Week 12 game against the Bills last year. 

The Chargers averaged 5.5 yards per carry, and they nearly ran their way to a win.

"It was disappointing there in that most of them were just — all of them really — were just fundamental errors on our part in calls that we play a lot," Fangio said. "That we played a lot prior to the first half when we were playing the run good and when we played the run better late in the game. We had a stretch there where fundamentally we were off. Obviously, when you do that, you're going to have problems, and we did have our problems."

The Broncos likely missed Mike Purcell, a stout run stopper who was injured against the Chiefs and placed on injured reserve with a season-ending injury ahead of Week 8.

Denver did get at least one needed run stop. On a fourth-and-1 from the Denver 26-yard line to begin the second quarter, Dre'Mont Jones knifed through the line of scrimmage to record a tackle for loss and a turnover on downs.

NOTHING SERIOUS

The NFL trade deadline is rapidly approaching, as teams must strike their desired deals by 2 p.m. MT on Tuesday.

Fangio said Monday that he had no indication that the Broncos would be active at the deadline.

"I haven't had any discussions with [President of Football Operations/General Manager] John [Elway] on that, which means, to me, that nothing has been talked about seriously enough or imminent enough that he thought worthy enough of bringing to me," Fangio said.

Denver has made a trade ahead of the deadline in each of the last two seasons, as the Broncos dealt Demaryius Thomas to the Texans in 2018 and traded Emmanuel Sanders to the 49ers last season.