Broncos at Bengals -- Week 9

Where: Paul Brown Stadium, Cincinnati (turf, outdoors)

When: Sunday, 1 p.m. EST (CBS)

Spread: Broncos by 4

Forecast: Mostly cloudy with a 10 percent chance of rain; 46-49 degrees

2012 records: Broncos (4-3); Bengals (3-4)

Past results: Two most recent meetings -- Sept. 18, 2011: Broncos 24, Bengals 22; Sept. 13, 2009: Broncos 12, Bengals 7. Series record: Broncos hold an 18-8 edge.

What matters: It feels like the Broncos have a commanding lead in the AFC West, but the truth is that they're only a half-game up on the San Diego Chargers, who might have saved their season with a 31-13 win Thursday against Kansas City. Denver's eight opponents in the second half of the season are a combined 20-40 right now. The Chargers have a tougher second-half slate -- but not too tough. Their next eight foes are a collective 26-33.

Overconfidence and a perception that the tough part of the schedule is behind the Broncos is only their second most dangerous enemy, ranking behind their continued propensity for fumbling. RBs Willis McGahee and Ronnie Hillman each fumbled last week. Hillman's bobble was harmless, as the ball skipped out of bounds; that was the first fumble the Broncos didn't lose all season. Nevertheless, Denver's 11 fumbles are a concern, and their 10 lost fumbles is second-worst in the league, only ahead of the calamitous Chiefs (15 lost fumbles).

Who matters: Denver's offensive line hasn't allowed a sack the last two games -- which, not coincidentally, is the only stretch of the season it's played with RG Chris Kuper, who missed Weeks 1-5 with a fractured left forearm. However, not everything is perfect; a missed protection by LG Zane Beadles and C Dan Koppen (who slipped on the play) led to a pressure on QB Peyton Manning from New Orleans DL Martez Wilson and S Roman Harper last week; Manning banged his right thumb on Wilson's helmet and was fortunate to emerge with damage to his thumbnail.

"Any time the quarterback gets hit, you think about things," offensive coordinator Mike McCoy said. "He's tough; he hung in there and made a hell of a throw. Unfortunately, we had a breakdown on protection, which we have to eliminate."

No one in the AFC has been better at exploiting protection breakdowns than the Bengals, who have 23 sacks this season, including seven by DT Geno Atkins. Denver's offensive line was exploited in the middle early in the season before Koppen replaced an injured J.D. Walton and Kuper returned, but he offers the sternest test they've faced since entering the lineup.

Key matchup: The one-on-one duel between Broncos CB Champ Bailey and Bengals WR A.J. Green could end up deciding the contest. Broncos defensive coordinator Jack Del Rio has moved Bailey around to shadow the opponent's top receiver most of the last four-and-a-half games, and Bailey has flourished. He hasn't permitted a catch longer than 25 yards this year and hasn't allowed a touchdown since Week 13 of last season, a streak of 13 consecutive games, including playoffs. Bailey's streak of not allowing a score will be tested by Green, who has at least one touchdown in six consecutive games.

"If I'm betting, I'm betting on (Bailey) -- if I was a betting man. Eleven Pro Bowls," said Broncos S Mike Adams. "I'll take my guy any day, no matter what receiver's out there."

But defending Green is a team effort. Cincinnati will try to force Bailey out of the play at all costs and set up matches with other cornerbacks -- particularly Tony Carter, who enters when the Broncos go into nickel packages. Carter is the Broncos' 'fastest defender but is also seven inches shorter and 32 pounds lighter than Green.

Injury of note: CB Tracy Porter was ruled out after not practicing Friday. Porter continues to struggle with symptoms, including dizziness that were a precursor to a seizure in August. He practiced on a limited basis Wednesday and worked through the full practice Thursday, which was his only full work since Oct. 13.

Inside stuff: Last week's balanced offensive performance -- 225 rushing yards on 42 carries; 305 passing yards on 30 attempts -- was more like what the Broncos wanted all along than the air-centric tactics they'd used most of the season, when they repeatedly fell behind in the first three quarters, usually by multiple scores. That balance also set up the Broncos for their longest gain against the Saints -- a 41-yard play-action pass from Manning to Demaryius Thomas that was preceded by four McGahee runs. If the Broncos can establish the run again early, they'll defuse the Bengals' pass rush, giving Manning more than enough time to execute play-action and wait for late-opening receivers downfield. That will also make the Broncos' offense nearly impossible to effectively stop, since their passing game flourished even when the offense was one-dimensional in losses to Houston and New England and the comeback win at San Diego.

Connections: Bengals TE Richard Quinn was released last year after spending two seasons (2009-10) with the Broncos. He was the last third of a disastrous class of 2009 second-round picks (Alphonso Smith and Darcel McBath were the others), none of whom is still with the team … Broncos WR Andre Caldwell was a Bengal for four seasons (2008-11) … Broncos DE/DT Derek Wolfe played at the University of Cincinnati from 2008-11 … Broncos C Dan Koppen was a teammate of Bengals RB BenJarvus Green-Ellis in New England from 2008-11 … Broncos LB Keith Brooking and Bengals CB Terence Newman were teammates in Dallas from 2009-11.

Stat you should know: The Broncos are 1-10 in their last 11 trips to the Eastern time zone, including two losses earlier this season at Atlanta and New England.

Record watch: If Manning throws for over 300 yards and three touchdown passes and completes at least 70 percent of his passes, he will extend his league-record streak of games reaching those milestones to five. No one else has ever done that more than twice in a row.

Looking ahead: November offers a chance for the Broncos to put .500 far behind them if they win Sunday at Cincinnati. Two of their following three games are against teams with just one win -- Week 10 at Carolina (1-6) and Week 12 at Kansas City (1-7). They sandwich a Nov. 18 game against San Diego that could allow the Broncos to practically lock down the division crown.

Prediction: Broncos 31, Bengals 16.

For up-to-the-minute Broncos updates, follow Andrew Mason on Twitter at @CBSBroncos.