Cardinals defensive coordinator Al Holcomb knows the 49ers – who visit State Farm Stadium Sunday – can run the ball, since San Francisco is second in the NFL in rushing and since the Niners gained 147 yards on the ground against Arizona in the teams' first meeting.

So Holcomb noted this week the Cardinals' defensive tackles need to play well.

Now we wait to see who those defensive tackles are, and how the playing time is broken down.

Starter Corey Peters is battling an ankle injury that will make him a game-day decision, and while Peters said he was optimistic about his availability, it seems crucial the Cards have him. Former starter Robert Nkemdiche is coming off the bench in favor of Rodney Gunter (Olsen Pierre is another in the rotation) while Holcomb mixes and matches.

"Well, it's really a next man up mentality more than anything," Holcomb said, talking about Gunter's ascension. "From a situational standpoint, we've been trying to figure out all season who the right players are, who will be in the mix.

"These are the guys that we have. We have to coach them and get them better. If one man is potentially not doing the things we need him to do, then we have to try the next man and keep turning it until we get it right."

Nkemdiche is still trying to find consistency, Holcomb said, although head coach Steve Wilks said he believed Nkemdiche was mentally "in it" all week.

"From the standpoint of the defensive line, particularly inside, all those guys play," Wilks said. "It's a strong rotation. (Nkemdiche) is definitely going to play this week and I look for him to be productive."

Nkemdiche said the coaches have stressed all week about inside penetration to impact the 49ers' run game, and getting vertical in the right spaces.

"I know there are some times I've gotten out of my gap … things happen," he said. "It's about staying consistent and staying technically sound."

The message to those playing couldn't be more clear.

"We have to be really sharp," Peters said. "Someone gets cut out of the middle, it creates a huge hole."

LEFTWICH TEACHING ROSEN ABOUT "THE TOUGHEST JOB IN SPORTS"

Offensive coordinator Byron Leftwich's 30,000-foot view of his job is simple – preparing Josh Rosen to be a successful long-term quarterback, at a position Leftwich called "the toughest job in sports."

"What we have to deal with and prepare for on a daily basis, you guys have no clue," Leftwich said. "Everything about this is tough. (Rosen) understands that. The kid works his tail off. Couldn't ask for a better guy from a going-out-every-day-and-getting-better standpoint. Hopefully we'll get him playing well."

Rosen said Leftwich has already been helpful in smaller ways, ways that Leftwich was already familiar having played QB in the NFL for a number of years.

"What he is helping me out with is being more refined and deliberate with rules, having harder rules on where to go (and) when, so that I can just go out there and play fast," Rosen said. "When I think less, I get to play a little quicker, play more efficient. He understands what it's like to be in an offense that might be a little too complicated or an offense that might be a little too simple. We are working together to try and find that sweet spot."

DAWSON STILL QUESTIONABLE, BOSTON OUT FOR SUNDAY

Wilks said kicker Phil Dawson (right hip) will be among those who will be a game-day decision, while safety Tre Boston (shoulder/ribs) and offensive lineman Jeremy Vujnovich (hamstring) will be out Sunday. The Cardinals did sign kicker Matt McCrane to the practice squad Friday and would have to get him to the active roster Saturday if they want to have him available for the game.

In addition to Dawson and Peters, tight end Jermaine Gresham (heel) is now questionable after being added to the injury report Friday as limited. Guards Justin Pugh (hand) and Mike Iupati (back) are also questionable.

For the 49ers, wide receiver Pierre Garcon (shoulder/knee) is doubtful, while running back Matt Breida (ankle), center Weston Richburg (knee) and cornerback Richard Sherman (calf) are questionable.