Brinkley gets shot to show he can cover

There have been worries about linebacker Jasper Brinkley's abilities in pass coverage. That was a major concern in July as the Vikings headed into training camp with Brinkley inked in as their starting middle linebacker. Now, with Erin Henderson ruled out for Sunday because of a concussion and Brinkley inheriting Henderson's snaps in the nickel defense, there will be plenty of pressure this weekend. Brinkley, who missed all of 2011 because of a hip injury, doesn't want to be pigeon-holed as a guy who is only reliable against the run. So here's his opportunity.

"This will be his chance to show his teammates along with everyone else that, 'Ya know what, I can do more than play on first and second downs,' " coach Leslie Frazier said Friday.

Keep in mind, the 49ers have one of the premier pass-catching tight ends in football. Vernon Davis has eight catches for 116 yards and three touchdowns already this season.

Marvin Mitchell, who will start at weak-side linebacker in place of Henderson, also will be under the microscope, seeing his first regular-season action with the Vikings.

Can the Vikings find a way to contain Justin Smith?

There might not be a defensive lineman in the NFL more consistently disruptive than Smith, a 12th-year veteran and three-time Pro Bowl player. Smith has started 173 consecutive games and remains a force up front in San Francisco's 3-4 defense.

"He's so strong," Frazier said. "And he plays so physical that it's hard to single-block him for any length of time. Even if you have pretty good position, he does a good job of using his hands, working his feet. And his power? It's impressive."

"We haven't seen anyone just block one guy on him and say, 'You're going to handle Justin throughout four quarters,'" Frazier said. "We don't think we're in that position either."

If you're into placekicking, Sunday's game should be a treat. San Francisco's David Akers led the NFL in scoring in 2011, making a league-best 44 field goals in 52 attempts. Akers started 2012 with even more fireworks, tying an NFL-record with his 63-yard field goal just before halftime of a Week 1 victory at Green Bay.

Vikings rookie Blair Walsh, meanwhile, has been plenty reliable himself. He has hit all six of his field goal attempts so far, including bombs from 55 and 51 yards in the first two weeks.

Walsh has also had 11 kickoffs this season with seven touchbacks and only one returned beyond the 20.

Chew on these statistics for a minute. San Francisco quarterback Alex Smith hasn't throw an interception since the first half of a Thanksgiving night loss to Baltimore last season. Smith has thrown just five interceptions in 502 passing attempts since the start of 2011.

So just how does Smith account for his noticeable growth the past two seasons?

"I'm not trying to do too much, which I had done in the past early on in my career," Smith said. "Just doing my job and not trying to force things."

Henderson's concussion is by far the most significant injury. The starting linebacker banged his head making a tackle on Indianapolis' second-to-last drive last weekend. He was formally diagnosed with a concussion Wednesday and will have to wait until next week for clearance.

The only other Vikings starters listed on the injury report are John Sullivan (ankle), Brian Robison (elbow) and Chris Cook (biceps), who are all probable.