Keys to the game: 49ers/Vikings

The 49ers look for their first 3-0 start since 1998 on Sunday when they play the Minnesota Vikings at the Metrodome in Minneapolis to complete their run of three consecutive games against NFC North opponents to begin the season. NinersDigest identifies the keys to the game and what the 49ers need to do to beat the Vikings for the first time since 2006.

Stuff Adrian Peterson and Minnesota ground game
It will be strength vs. strength when the NFL's best rushing defense matches up against a Minnesota rushing attack that has been one of the league's best for the past several seasons with Peterson leading the way. The Vikings finished fourth in the league in rushing and second in rushing average last season, and they bring a two-headed attack with Peterson and Toby Gerhart, who have combined for 177 yards rushing so far as the Vikings have attempted to balance their offense through the first two games. They would like to keep that balance going this week – Minnesota is actually higher in the NFL rankings in passing (13th) than it is in rushing (14th) – but the Niners can wrench what the Vikes want to establish on offense by doing what their defense does best against what figures to be one of the top rushing games San Francisco will face this season.

Expose the weaknesses in Minnesota defense with passing matchups
The 49ers went right at the weaknesses in Detroit's defense last week with immediate results. With injured starters missing in the Detroit secondary, the 49ers challenged their replacements from the start, and that resulted in a four-play touchdown drive on San Francisco's first offensive possession, with tight end Vernon Davis burning backup safety John Wendling for an easy 21-yard touchdown reception. The Vikings this week will be without top linebacker Erin Henderson, who will miss the game because of a concussion, and that is a big loss for a young and rebuilding Minnesota defense that has gotten off to a promising start. Henderson had been remaining in the game in passing situations as part of the Vikings' nickel coverage packages, and his absence will put more pressure and responsibility in the passing game on middle linebacker Jasper Brinkley, whose strength is in stopping the run.

Vernon Davis vs. Chad Greenway
While the Niners look to expose those weaknesses mentioned above, one of the key matchups in the game will be San Francisco's explosive tight end against one of the few outside linebackers in the NFL who might actually be able to cover him. Greenway, who went to the Pro Bowl last season and is one of the NFL's top tacklers over the past two seasons, is an athletic edge player and one of the key performers in making the Minnesota defense tick. He has the size and speed to stay with Davis and likely will have the responsibility of covering him in several defensive matchups. Davis already has caught three touchdown passes this season and, against the Lions, showed that he can toast teams that attempt to cover him with smaller safeties. The Vikings will look to Greenway to help keep Davis out of the end zone this time.

Limit Minnesota's underneath passing game
While the 49ers will look to stick Minnesota with an underneath passing game, the Vikings will try to do the same to San Francisco. The short and intermediate passing game has worked well for the Vikings so far and has helped Minnesota establish its offense so far during the young season. Quarterback Christian Ponder completed 12 passes to Percy Harvin in last week's narrow loss to Indianapolis, but Harvin averaged just 8.7 yards per catch as the Vikings took what the Indy defense was giving them. They'll look to do the same here against the 49ers with Ponder, who completed 27 passes against the Colts but averaged just 9.1 yards per completions as the Vikings averaged just 5.9 yards per pass play.

Cut down sacks on Alex Smith and give him time to get in a rhythm
Smith has found time to get in a passing rhythm during San Francisco's first two games – that's why he's the NFL's second-ranked quarterback this week with a passer rating of 115.9. But he also has been sacked seven times in those games and is on a pace to be dropped 56 times this season after being sacked more times than any other NFL quarterback in 2011. That's a trend that the 49ers must end – and soon, as in now. Since the start of last season, Smith has been sacked 51 times, again the most of any NFL QB over that span. He's been able to remain healthy despite absorbing that punishment, but the Niners can't allow him to keep getting hit that often. That becomes of particular importance Sunday against the Vikings, who tied for the NFL lead with 50 sacks last year and feature a premier pass rusher in right end Jared Allen, who led the NFL with 22 sacks last year. Allen often will be matched up against left tackle Joe Staley, who had his problems two weeks ago with another premier pass rusher, Green Bay's Clay Matthews.

Pressure and pick Ponder
In his second NFL season, Christian Ponder is off to a fine start and has settled into a steady groove as Minnesota's starting quarterback. The Niners need to unsteady that progress and knock Ponder out of that groove. Ponder leads the NFL with a completion percentage of 75.8 and his 110.6 passer rating ranks sixth in the league. He has been perhaps the key player in Minnesota's offensive improvement so far this season and has yet to throw an interception in 62 attempts after throwing 13 picks in 10 starts as a rookie. He also had some success against San Francisco's first-team defense in the preseason opener back in August, connecting on a 52-yard pass on Minnesota's second offensive play. Ponder was sacked four times last week against the Colts, however, and the Vikes trailed 20-6 entering the fourth quarter before Ponder finally got going with two late touchdown passes. The Niners can go a long way toward disrupting the Vikings by pressuring Ponder and forcing him into turnovers for the first time this season.

Win in the return game
The Niners were of the NFL's best in returning kicks and punts last season, which was a big reason for their surprising 2011 turnaround. But so far this season… not so good. The 49ers rank just 25th in the NFL in kickoff return average after leading the league in that department last season, and besides an inconsequential 20-yard return in the season opener, Kyle Williams has done little as the team's punt returner in place of the injured Ted Ginn Jr. The Niners need to do better Sunday, or at least well enough to give San Francisco an edge over the Vikings, who also feature an explosive return game that ranked second in the NFL last year in kickoff returns. Percy Harvin is particularly dangerous on returns and currently ranks third in the NFC with a 33.2 average returning kickoffs. Top Stories