ENGLEWOOD, Colo. -- Boxer Mike Tyson used to say, "Everybody has a plan until they get punched in the mouth."

That was the case for the Denver Broncos, who certainly had a plan on defense coming into the season -- a plan built around coach Vic Fangio's arrival -- but that was before all the injuries.

"You adjust," Fangio said. " ... That's part of the NFL, things happen, you adjust."

Even with the injuries and adjustments, the Broncos are still a top-tier defense. They rank No. 11 in total defense (324.3 yards allowed per game), No. 9 in scoring defense -- as one of nine teams giving up fewer than 20 points per game -- and No. 5 in pass defense. Keeping those rankings down the stretch will be no small feat with trips to Houston and Kansas City, but the marvel is that they've done so well up to this point.

"I know it's kind of the cliché, or the boring answer, but it really is the next man up," safety Justin Simmons said.

Fangio said he has had the "perfect world" scenario at times in his career, when the scheme fits the personnel and injuries are mostly avoided. He said "we had it last year in Chicago," when the Bears finished No. 4 in total defense, No. 1 in scoring defense, No. 1 in interceptions and No. 1 in takeaways overall with Fangio as the defensive coordinator.

It hasn't been perfect for the Broncos. It started with cornerback Bryce Callahan limping off the field during a July stadium practice in training camp. Callahan didn't play a snap this season before he was moved to injured reserve Nov. 16. Callahan had been signed, as a former Bears cornerback in Fangio's time there, to a three-year, $21 million deal to start for the Broncos.

Then Bradley Chubb, who had 12 sacks as a rookie last season, went to injured reserve Oct. 1 because of a torn knee ligament. Cornerback De'Vante Bausby, an Alliance of American Football find as well as a bit of a revelation as Callahan's replacement, went to injured reserve seven days after Chubb because of a neck injury.

And Derek Wolfe, who has had all seven of his sacks in the past six games and leads the team, went on injured reserve this week.

Toss in a bit of a carousel at cornerback to go with Von Miller's recent knee troubles and you have almost a down-to-down, mix-and-match approach where most anybody left in uniform is the proverbial next man up.

"It's kind of amazing," linebacker Todd Davis said. "If you do look at some of the young guys who came in and are making plays and making names for themselves, I think that it shows the depth that we have on this defense, but also that we're fighters."

Said Fangio: "You don't change a whole lot, you just might major in other stuff, if you know what I mean, in the package more-so than if you had all the guys. I guess in some ways it's a change, but you're not revamping or overhauling, a balanced package has everything in it, but sometimes you're going to have personnel issues where you're majoring in something you'd rather not because you're forced to."

The Broncos have played their nickel package -- five defensive backs -- most this season. At the start of the season, when the Broncos were adjusting to Callahan's absence, safety Kareem Jackson played as the nickel cornerback, matching against the slot receivers. But Jackson's move back to safety has settled things in the secondary. And without Chubb for all but four games, the Broncos have largely stuck to a four-man pass rush -- though they have mixed and matched the four with defensive backs and linebackers jumping in as another player drops into coverage.

They've rushed four on 72% of opposing quarterbacks' dropbacks, including penalty snaps, and only a handful of snaps (five) when they've rushed at least six. Fangio said this week he would rush five or more at opposing quarterbacks more often if the Broncos were at full strength.

"Everybody likes to pressure, but I like to pressure when I want to pressure, not because I have to pressure, I want to call the game the way I see fit to call it," Fangio said. "... Your first inclination with any of it, injuries and other things, is you get frustrated, for a couple seconds, but then you get over it, because you have to. There are games to be played, guys have to get ready, everybody has to do their jobs, so you're quickly over it, and get to work."