For the first time since Aldon Smith entered the NFL in 2011, the 49ers played a game Sunday without Smith and NaVorro Bowman.

So what did their defense look like without two All-Pro linebackers?

Surprise: It wasn’t as good.

The 49ers’ four first-half takeaways did allow them to cruise to a 28-17 win, but it somewhat obscured holes in their run defense: Dallas running back DeMarco Murray had 118 yards on 22 carries and averaged 5.4 yards an attempt.

Murray probably benefited from running against a defense poised for passing. After all, 17 of his carries came after the Cowboys were trailing 21-3 in the first quarter. Still, players acknowledged it’s an area that needs to improve.

Consider: Murray became the first running back since 2009 to average more than 5.3 per attempt with at least 20 carries against the 49ers.

“I think we’ve just got to get getter at playing together,” said linebacker Dan Skuta, who started in place of Smith. “I think that showed up in the run game and with our pass rush. Just kind of being used to each other and playing well together takes a few games. And you don’t quite get that all the way through preseason because you’re mixing and matching so much. That will just come with a little bit of time.”

The 49ers realize they’ll need to hurry.

Starting with Sunday night’s meeting against the Bears and running back Matt Forte, they’ll face the NFL’s top three rushing leaders from 2013 over the next four games.

Philadelphia’s LeSean McCoy (Week 4) ranked first, Forte was second and Kansas City’s Jamaal Charles (Week 5) was third in 2013. That versatile trio combined for 6,059 total yards, 196 receptions and 42 touchdowns last year.

All-Pro defensive tackle Justin Smith (6 tackles, 2 sacks) appeared to do his part to fill the void Sunday, but said the entire unit had to improve.

“When you’re missing guys like Aldon and Bo … you’ve got two legitimate year-in and year-out defensive players of the year,” Smith said. “We’ve all got to step up. All 11 of us.”

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Since 2004, the running backs who have averaged more than 5.3 yards attempt with at least 20 carries against the 49ers:

Shaun Alexander (Seattle), Nov. 7, 2004: 26 carries, 160 yards, 6.2 YPC

Ryan Grant (Green Bay), Nov. 22, 2009: 21 carries, 129 yards, 6.1 YPC

Willie Parker (Pittsburgh), Sept. 23, 2007: 24 carries, 133 yards, 5.5 YPC

Chris Johnson (Tennessee), Nov. 8, 2009: 25 carries, 135 yards, 5.4 YPC

DeMarco Murray (Dallas), Sept. 7, 2014: 22 carries, 118 yards, 5.4 YPC

Source: Pro Football Reference

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The 49ers banged-up secondary got a bit of good news via Twitter on Tuesday.

In a now-deleted post, rookie cornerback Jimmie Ward said he did not sustain a concussion against the Cowboys.

That presumably means Ward will be in action against Chicago.

The status of cornerbacks Tramaine Brock (sprained toe) and Chris Culliver (concussion) remains in question. On Tuesday, Culliver said he couldn’t speak with reporters until he was medically cleared.

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Practice-squad defensive lineman Lawrence Okoye said he’s been moonlighting on the offensive line because of injuries, but there are no plans for him to make a position switch.