Vikings defenders have been a band of marauders the past two weeks. The Vikings have surrendered just 2.9 yards per rush attempt and forced five turnovers while posting back-to-back victories.

Now, this Sunday, Minnesota's defense faces an intriguing test, against future Hall of Famer Peyton Manning and the 3-0 Denver Broncos.

Wondering how good the 2-1 Vikings truly are? Here's the litmus test.

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Let's take a closer look at this Sunday's showdown in Denver, in which the Broncos are favored by 6.5 points.

3 THINGS TO WATCH

-- Peyton Manning's arm. The Broncos are still implementing a new offense under their new head coach, Gary Kubiak. The new offense often utilizes snaps taken from under center (as opposed to Manning's preferred shotgun looks). Kubiak's scheme often requires Manning, 39, to throw on the run, which isn't his strength. Manning, averaging 251.6 passing yards per game, has looked like a relatively average QB this season, and the Vikings have produced two interceptions and three fumble recoveries over the last two games. This should make for an interesting, early season exam for young Vikings defenders like safety Harrison Smith.

-- Adrian Peterson's feet. The Vikings' star enters Week 4 leading the NFL in rushing, with 291 yards. The 30-year-old has produced back-to-back 100-yard rushing games for the first time since 2013, and is averaging 4.9 yards per carry during this young season. Last week, Peterson unleashed a vintage, 43-yard touchdown run. He might find the footing a bit treacherous in the Mile High City, though; the Broncos' run defense yields just 82.7 yards per game this year.

-- Teddy Bridgewater's progress. It was hard to find fault with much in the Vikings' 31-14 defeat of San Diego last week. Bridgewater was the exception. Minnesota's 22-year-old QB threw for just 121 yards versus the Chargers, serving in a game-manager role. This week, he may have to step up his production. Since 2012, Denver is 6-0 at home against NFC foes. Bridgewater's recent dink-and-dunk passing might not cut it this week. He would benefit from a breakout performance from pass-catchers like Mike Wallace or Kyle Rudolph. The bad news: Denver's pass defense (176.3 yards per game allowed) is ranked No. 1 in the NFL, and pass-rusher DeMarcus Ware (3.5 sacks) is in All-Pro form this season.

2 THINGS TO REMEMBER

-- Neither the Vikings nor the Broncos have allowed a single point in the first quarter of games this season. If Minnesota falls in an early hole, can it recover? That certainly wasn't the case in Week 1 on the road, near the start of an eventual 20-3 Vikings setback in San Francisco. The 2-1 Vikings are off to their best start after three games since 2012; getting off to a solid start in this game could be a key to Minnesota continuing its recent success.

-- The Vikings and Broncos usually play airtight contests when they square off. The Vikings narrowly lead their all-time series with the Broncos, 7-6. Denver, however, has claimed the last two meetings, winning both games by a field goal on the last play of the game. Among the 13 previous meetings between Minnesota and Denver, seven have been decided by a field goal or less -- and 12 have been decided by eight points or less. If history is any indication, this Week 4 contest could come down to the wire.

1 KEY MATCHUP

Vikings secondary vs. Peyton Manning

This game should be all about Mike Zimmer matching wits with the veteran guile of Manning. In the past two weeks, Minnesota has held opponents to 15.0 points per game, as Zimmer, Minnesota's second-year head coach, has used a mix of blitz packages to harass opposing quarterbacks. Manning, in his 17th season in the league, won't be as easily befuddled. Vikings pass rushers like Everson Griffen (3.0 sacks in 2015) and Anthony Barr (1.0) will have to be disruptive. Manning won't lack for motivation, however, as the veteran seeks his 100th career regular-season win at home -- in NFL history, only Brett Favre (113) produced more home wins in his career.

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