But really, the game was never that close. San Diego's much-maligned defense held the NFL's top-rated offense, on its home field, to season lows of 20 points and 295 total yards.
In a short week, Chargers defensive coordinator John Pagano put together a masterful game plan. At times the Chargers seemed like they were in Denver's huddle, anticipating when quarterback Peyton Manning would check down or when he would audible to a run at the line of scrimmage.
The Chargers played mostly nickel defense, with five defensive backs. With regular nickel cornerback Johnny Patrick out due to an ankle injury, safety Marcus Gilchrist moved back to the position he manned his first two years with the team and Jahleel Addae took his spot at safety.
Gilchrist was active, finishing with six tackles and a sack.
"Some of the disguises, it looked like to me from the sideline, were really beneficial," San Diego quarterback Philip Rivers said. "[Eric] Weddle was all over the place, along with Donald Butler. Gilchrist played the nickel today, which was kind of his home from years past. And I think he had a heck of a game."
Denver came into the contest No. 1 in the NFL in third-down efficiency, but the Chargers held the Broncos to 2 of 9 (22 percent) on third down. San Diego forced Denver into three consecutive three-and-outs at one point.
"We just watched film and did a lot of walk-throughs," said cornerback Shareece Wright, who finished with team highs of seven tackles and two pass deflections. "We focused a lot on watching film, and just knowing what they did to us the first game. When you play a team twice, you better be ready the second time."
The Chargers defeated a Manning-led Denver team for the first time Thursday. San Diego also snapped Denver's 10-game win streak in AFC West contests since Manning came aboard last season.
For the second straight game against Denver, the Chargers held the ball for more than 38 minutes. But unlike the earlier game, a 28-20 loss, San Diego finished drives with touchdowns, grabbing a 24-10 lead early in the third quarter and holding off a late Denver rally.
"We didn't have the ball much," Manning said. "And when we had it, though, we didn't do enough with it. Give San Diego credit, they played better than we did."
Offensively, the Chargers rode the wide shoulders of running back Ryan Mathews, who topped the 1,000-yard mark for the second time in his pro career. Mathews rumbled for 127 yards on 29 carries, including a 23-yard touchdown run. Mathews now has 1,012 yards with two games left to play.
"We just wanted to establish the run," Mathews said. "We've got big, good guys up front. And they were just working their tails off. And for how hard they work, you really want to succeed for them. So I was trying my best to get positive yards every play."
Rivers threw for only 166 yards, but he was efficient, finishing 12-of-20 with two touchdown passes, no interceptions and a 120 passer rating.
San Diego coach Mike McCoy joked about a misunderstanding that led some to think he guaranteed a victory over the 11-3 Broncos, saying he and Denver executive John Elway shared a laugh about it before the game.
But McCoy remained steadfast in the belief that his team could beat the Broncos, one of the favorites to win the Super Bowl.
"I've never gone into a game that I did not think the football team I was either playing or coaching on wasn't going to win," McCoy said. "I'm not saying it's a guarantee, but that's the confidence I have as a player and as a coach, and in the players I have in our locker room."
At 7-7, the Chargers are back into the hunt for the final AFC wild-card spot. But even if they win out, San Diego will still need some help from other teams around the league.
"It's just staying alive," Rivers said. "We know that we need help. We obviously know that we have to win the next two, and then we need some help. But we've just got to keep it one game at a time, and enjoy the heck out of the turn we've made. And see if we can keep it going."