Rex Ryan rips the Browns after their loss to the Broncos and for mishandling their roster. (1:00)

ENGLEWOOD, Colo. -- Denver Broncos coach Vic Fangio believes in roll-up-your-sleeves effort, but also in very simple math.

On Sunday, the Broncos limited the Cleveland Browns to one touchdown in five trips inside the Broncos' 20-yard line -- instead forcing field goals on three of those drives. They held the Browns to a field goal on another drive that ended at the Broncos' 21-yard line and had a fourth-down stop at the Broncos' 5-yard line. They won the game by five points.

"You can do the math," Fangio said. "Three instead of seven, one time zero instead of three or seven. That's the difference in the game."

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Amid a sea of troubles during a 3-6 start, the Broncos' red zone defense over the past six games has been a raft to cling to.

They have limited teams to touchdowns on 37% of drives inside the 20 -- second-best in the league behind the undefeated San Francisco 49ers.

It didn't start that way, though. During the season's first three games, opponents scored touchdowns on six of their seven trips inside the Broncos' 20-yard line. But over the last six games, opponents have scored touchdowns on just 4 of 20 trips (20%) inside the Broncos' 20-yard line.

The Broncos are 3-3 during those six games, with a loss to the Jacksonville Jaguars on the final play to go with a loss to the Indianapolis Colts on a kick with 22 seconds remaining.

"Just tighten up the coverage down there, play a lot better, do whatever you got to do to keep them out of the end zone," said cornerback Chris Harris Jr. "We've made some plays down there. ... The red zone is win or lose for us."

The Broncos' current red zone success is somewhat historical for the team. Since 1999, the season following the Broncos' second of back-to-back Super Bowl victories, the Broncos have not finished a season below 40% in red zone defense, but they're on pace for that now. In fact, they've been over 50% in 15 of those years and over 60% four times, including 61.7% in 2013, when they advanced to Super Bowl XLVIII.

"Our guys have just played good down there," Fangio said. "We've hung in there versus the run, which is important down there, we try to vary our coverages. And we put a lot of time into it in preparation."

There are plenty of other items on the Broncos' to-do list overall, but until the team's offense can find a few more plays like it had in Sunday's win over the Browns -- rookie tight end Noah Fant had a 75-yard catch-and-run touchdown and running back Phillip Lindsay had two of his four longest runs of the season -- the Broncos will have to try scratch out wins in every way possible.

One of the keys has been the Broncos' ability, at times, to limit opponents' rushing production in the scoring zone despite being in their nickel (five defensive backs) and dime (six defensive backs) looks. Fangio has also singled out Harris as well as safeties Justin Simmons and Kareem Jackson for their play while getting some good work from cornerback Davontae Harris and cornerback Duke Dawson Jr., who weren't even on the roster before Aug. 31.

Defensive end Derek Wolfe said "it's Vic's defense ... the bottom line. We're in the right spots for a lot of things we see. We can always be better, but it's coming around."