SANTA CLARA -- Head coach Kyle Shanahan believes the 49ers have a sizable advantage over the Arizona Cardinals on Sunday at Levi’s Stadium.

The 49ers face a rookie quarterback, Josh Rosen, making his second career start, and a running back, David Johnson, who piled up more than 2,000 yards from scrimmage in 2016 before a wrist injury limited him to just one game last season.

But it all starts with the 49ers’ defensive line against the Cardinals’ offensive line. Shanahan said he believes that matchup is where his team should make an impact.

“I think it’s a big week for our D-line,” Shanahan said on “49ers Game Plan,” which airs every Saturday evening on NBC Bay Area.

“I think they should be able to win their battles. If they play as well as they can, they should have a good matchup against Arizona’s O-line, and I think they should take some of the pressure off our linebackers. And, hopefully, when that happens, our guys can run around and make some plays.”

Inside linebackers Fred Warner and Reuben Foster will have the challenge of covering Johnson out of the backfield. Johnson caught 80 passes for 879 yards and four touchdowns in 2016.

Shanahan said he expects a lot from the defensive line to help out the two young linebackers.

“When it comes to David Johnson and our man coverages, I put a lot of pressure on our D-line this week,” Shanahan said. “If we let him run routes too long in man coverage, I don’t care who’s covering him, he’s going to win. And in the run game, if he gets to our linebackers untouched at 4 yards, they’re going to be able to continue to run the ball.”

 

Shanahan also expects the 49ers’ defensive line to apply pressure on Rosen without defensive coordinator Robert Saleh being forced to call on extra pass-rushers. Shanahan said he would like to see the 49ers make things difficult on Rosen with their coverages.

“It’s funny because usually the standard thing is to just pressure the rookie,” Shanahan said. “That’s what I hear from defensive coaches a lot. That’s always the first thing I hear people say, ‘How should we play this rookie? We should pressure him, right?’

“I’ll never give an absolute answer – it depends on the guy – but a lot of times I want to see a defense make a quarterback play quarterback. And what I mean by that, is I want to see a guy play in the pocket, go through progressions and have to get to two in a progression, three in a progression, see nobody’s open and get to No. 4 and check it down. Sometimes when you just blitz a rookie, No. 1 is open. He’s just running a slant, and it’s man-to-man, and if that guy just beats the corner, then it’s a route on air.”