Heading into their Week 9 bye, the San Francisco 49ers' defense appeared to be reeling a little after giving up 852 yards over the course of defeats to the Minnesota Vikings and Cincinnati Bengals, which took a losing streak that started with a last-second defeat to the Cleveland Browns to three games and led to pertinent questions being aimed in the direction of coordinator Steve Wilks.

One headline decision the 49ers made in response was to move Wilks from the booth to the sideline to better communicate with his players, the other was to strike a blockbuster trade deadline move for edge rusher and former second overall pick Chase Young.

The results have been spectacular. Since Week 10, the 49ers have allowed just 13 points per game as San Francisco has reeled off five successive wins to surge to the top of the NFC at 10-3. The 49ers' defense is ranked fourth by DVOA, its upturn only overshadowed by the remarkable consistency of an ultra-explosive offense that is earning increasingly frequent comparisons to the 2016 Atlanta Falcons attack coordinated by Kyle Shanahan.

Shanahan explains the surge

While the resurgence coincided with Wilks moving to the sideline, Shanahan sees it as correlation rather than causation.

Speaking in his Friday press conference ahead of the 49ers' Week 15 road game with the Arizona Cardinals, Shanahan was asked about Wilks' switch and how the defense has improved since the bye.

“Well, not because Steve is down there. I’ve loved him down there," he replied. 

"I think he likes it down there too. But I think, I’ve said this before, but I think we’ve been playing as a group better on all three levels. 

"I think even in our five wins in a row [to start the season] to our three losses, I just think it was a little sporadic. The D-Line had their times, the linebackers had their times, the secondary did. 

"I feel all three of those units have been just on all three levels have been matching each other better. That’s led to more turnovers. It’s led to more sacks. It’s led to a lot more PBUs and it’s been awesome having him down there too."

A test of cohesion

The cohesiveness Shanahan spoke of may well be tested this week. 

The 49ers will be without both their starting defensive tackles, Javon Hargrave and Arik Armstead. At linebacker Dre Greenlaw is questionable but is expected to play despite hip and ankle injuries while Oren Burks, the Niners' starter at SAM linebacker on base downs, is out with knee tendinitis. In the secondary, top cornerback Charvarius Ward did not practice all week because of a groin injury and is questionable.

Such a number of injuries could be seen as enough to disrupt the 49ers' upward momentum on defense in a matchup with a dual-threat quarterback in Kyler Murray who has previously caused San Francisco great problems.

But the 49ers had no issues after Hargrave and Ward left last week's win over the Seattle Seahawks and, regardless of whether his position in the stadium is having an impact, it will be another feather in the cap of Wilks if he can oversee another complete performance from an undermanned unit that helps the Niners clinch the NFC West.

49ers defense undermanned for tricky Cardinals test

They’re depleted at a key spot.