By Lyle Fitzsimmons, Contributing NFL Editor

(Sports Network) - If it's not already been done, let's go ahead and label the Peyton Manning experiment a success.

The Denver Broncos, who advanced to the playoffs last season on miracles, mirages and impeccably timed opposition missteps, are looking like a much more certain commodity this season.

And while ex-starter Tim Tebow is mired in anonymous locker room sniping along the East Coast, that same Mr. Manning has the orange within striking range of full-scale domination of the AFC's West Division.

Denver can go three games up on the team perceived to be its sturdiest challenger -- the San Diego Chargers -- when the Broncos host them on Sunday at Sports Authority Field at Mile High.

The hosts have won four straight games since a 2-3 start, the most important of which may have been the 35-24 defeat of the Chargers in San Diego that saw Denver climb from a 24-0 halftime hole.

The Chargers have won once in three games since -- against the last-place Kansas City Chiefs.

"Denver's playing amazing right now," San Diego safety Eric Weddle said. "All three phases are playing well off of each other and it shows on the tape."

Manning has emerged as a frontrunner for another MVP award -- he already has four -- with a 108.0 passer rating and a career-best 69.7 completion percentage.

He leads all players in fan-based Pro Bowl voting with 376,981 votes, more than 30,000 ahead of New England's Tom Brady and 43,000 up on Houston running back Arian Foster.

Balloting will conclude Dec. 17.

On the other side of the ball, the defense is sixth in the league, has allowed less than 19 points per game in the win streak and has dropped the opposing quarterback 12 times in the last two weeks alone.

Not to mention special teams, on which Trindon Holliday has run back kicks for touchdowns for two straight games as well.

Meanwhile, San Diego routed the Chiefs two weeks ago, but lost a chance to stay closer to the Broncos by frittering away a second-half lead last week in Tampa Bay.

Quarterback Philip Rivers was intercepted twice after halftime. One was returned for a fourth-quarter TD.

"The big negative plays, the turnovers are killing us," coach Norv Turner said. "Our biggest thing is we need to go put four quarters together, play at a high level, take care of the ball and not give up. If a team's going to make plays on you, make them earn it. Don't give up easy plays. It's a challenge for us coming into Denver."

Rivers has had career-long success in Denver -- winning five of six starts there -- but his 56.5 passer rating in the fourth quarter of games this season is poor, and his six interceptions in those situations are a league-worst. A late pick against the Broncos in the initial meeting was returned for a score by Chris Harris.

Conversely, Manning has a 121.9 rating in the last quarter, with nine touchdowns and no interceptions.

He's climbed within one scoring pass of tying Dan Marino for second in NFL history and has been sacked just 11 times this season, thanks to an offensive line particularly vital to his post-injury success.

"They have done a great job and certainly every quarterback appreciates it when you don't get sacked," he said.

Rivers, who's been dropped 22 times overall -- but only four in the last three games -- could be the target this week of Denver's Von Miller and Elvis Dumervil, who've combined for 17 sacks. Dumervil is questionable, however, after a shoulder injury last week. Back in the fold will be linebacker D.J. Williams, who's missed all nine games with a combination of off-field suspensions.

Chargers running back Ryan Mathews is also questionable with a stiff neck.

Elsewhere, San Diego tight end Antonio Gates has four TDs in his last four games and scored twice in the initial game with the Broncos last month. He's one score from equaling Lance Alworth's team standard of 81.

The Broncos lead the historic all-time series, 56-48-1, and have won two straight, though the Chargers had taken four in a row at the midway point of last season. San Diego's Turner is 8-9 in his career against Denver, while Denver's John Fox is 3-2 against the Chargers.

WHAT TO WATCH FOR

Denver has never beaten Rivers twice in any season in which he's been the starter, and forcing him into the same mistakes he made in the October game will be vital in ending that streak.

As recent history shows, he's simply not the same quarterback when he's being consistently harassed. The Broncos sacked Rivers four times in San Diego and enter this week as the league's overall leader with 31. They're also sixth in the NFL in interceptions with 10. Rivers passed for 337 yards against a sturdy Tampa Bay defense last week -- but eventually threw the two late picks that sealed the loss.

OVERALL ANALYSIS

The Broncos have surprised the most cynical of NFL observers this season, with Manning's better-than-anticipated return and the continued high-level play of a defense that was key to Tebow's success last season. In front of a home crowd and with the atmosphere jacked up closer to playoff intensity, they should avoid the 24-point deficit this time en route to a grinding, decisive and season-defining win.

Sports Network predicted outcome: Broncos 20, Chargers 17