For the Washington Redskins to defeat the San Francisco 49ers on Sunday, it's going to take more than just X's and O's when dealing with one of the league's top statistical defenses.

As they take the field for the first time at Levi's Stadium, the Redskins will be battling the fourth-ranked defense in the NFL in terms of yards allowed per game (308.8). And while the 49ers may be missing some key pieces on defense, Redskins left tackle Trent Williams believes the numbers don't lie.

"Even though they don't have those guys they that they had last year like Bowman and Willis and Wittman, obviously what they do have has been able to step in and play at a high level," Williams said.

While the 49ers searched for players to step up, rookie linebackers Aaron Lynch and Chris Borland were able to fill the voids. Lynch has recorded three sacks in the past four weeks while Borland leads the team in total tackles with 67, including a combined 48 tackles and two interceptions in the past three weeks.

The young 49ers linebackers have proven they are able to step in right away and produce, catching the eye of Redskins tight end Niles Paul, who anticipates a stiff challenge from that unit on Sunday.

"The 49ers, their backup linebackers are good," Paul said. "All we can focus on is executing our plan and hopefully making some big plays."

In general, Paul had some high praise for San Francisco's defense.

"Very good defense, probably one of the better defenses we've faced this year," Paul said. "Their front four is amazing and we're just going to have to be real good this week."

Up front, San Francisco boasts one of the league's top pass rushing defenses with 32 sacks on the year. Along with Justin Smith, Ahmad Brooks and Ray McDonald, the 49ers returned one of their best pass rushers last week in Aldon Smith, who was suspended the first nine games of the year.

With Williams' status for the game in question, rookie tackle Morgan Moses is preparing himself for the start. Should he get the nod on Sunday, he'll be going face-to-face with Smith, an All-Pro outside linebacker.

Although Smith has been able to put just one game on tape this season, Moses has been able to turn to veterans along the offensive line for tips and advice.

"I have guys like Trent and Tyler [Polumbus] who've played against him in previous years to help me feel him out during film study," Moses said. "It's just one of those things where you got to hit the film and look at him through the games that he has played."

For all the talk the 49ers' front seven has garnered around the Redskins' locker room, their defensive secondary has proven to be stout, as well. Currently ranked fourth in the NFL with 220.2 pass yards allowed per game, it's an experienced bunch led by nine-year veteran safety Antoine Bethea.

No matter where you look, head coach Jay Gruden says, the 49ers have talent on defense.

"They have solid players all across the board and then the second is doing an outstanding job too with the coverage," he said. "They give you a lot of different looks but consistently they stop the run and force you into some third down and longs and make it tough on with the amount of coverages they play."

In his weekly press conference on Wednesday, quarterback Robert Griffin III made it clear that the Redskins are focused on San Francisco. As they venture into Levi's Stadium for the first time on Sunday, Griffin III said he knows the talented 49ers derense "make youe arn every single thing you get."

"They don't give up a lot of plays and they play with passion," Griffin III said. "So we are going to have to match that going into their house and they are not going to make it easy for us."

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