The list of reasons Pro Bowl linebacker Marcus Washington enjoys switching from a 4-3 formation to a 3-4 scheme on defense is long, but there is no disputing what appeals to him most.

"I like [linebacker] LaVar [Arrington] being in there, that's what I like about it," Washington said. "It's kind of easy when you've got somebody who's able to get back there and disrupt a lot of plays. I think he's a key part of that 3-4 defense, because of that pressure he can provide."

The Redskins (4-2) used the defense regularly in Sunday's 52-17 trouncing of San Francisco, and it could figure prominently in this weekend's NFC East clash with the New York Giants (4-2) as well. After being benched for two games on defense, Arrington, a three-time Pro Bowler, was on the field frequently against the 49ers, almost always when the Redskins had four linebackers on the field.

Washington's basic defense is a 4-3, with four down linemen and three linebackers -- starters Warrick Holdman, Lemar Marshall and Washington -- but in the 3-4, a lineman comes off (usually tackle Joe Salave'a on Sunday), with an extra linebacker added (usually Arrington and sometimes Chris Clemons).

"There were some good things in the 3-4 and there were some bad things," defensive coordinator Greg Blache said. "On their first touchdown we were in that package, so it's not going to get straight A's. It's got its pluses and got its minuses like everything we do. It's a part of who we are -- it's not our essence -- and at the times it's conducive for us to use it, we're going to use it."

Arrington, 27, had several tackles for losses in the formation, including dropping running back Kevan Barlow for a four-yard loss on the final play of the first half and tackling wide receiver Rasheed Marshall for a seven-yard loss on a reverse early in the third quarter. Arrington, who missed almost all of last season with a knee injury, led the Redskins with nine tackles in the game, playing mostly on second and third downs. He is still not practicing with the starters and might not for some time, team sources said.

"My impression was he made some plays," Coach Joe Gibbs said of Sunday's performance. "I think he had his best week of preparation."

In the previous four games the Redskins did not use the 3-4 much. Arrington played a total of seven defensive plays over those games and never more than five in any contest. He was in for about 25 plays against the 49ers.

"The 3-4 requires everybody to be where they're supposed to be because you've got to compensate for one less D-lineman," Arrington said. "I like the defense. They move me all around, and that's kind of how I was used in college. Defenses never want the offense to know where the blitz is coming from."

The Redskins did not cause a turnover and had a total of two sacks in their four previous games, but caused two turnovers and had five sacks Sunday. Part of that was because of San Francisco's woeful offense, but the move to the 3-4 also allowed the coaches to get more playmakers on the field. Washington and Arrington, for example, are able to cover receivers on pass plays and are also effective rushing the passer like a defensive end.

"That's what makes it cool because we can switch it up and do a lot of different things with it, and they can't really key on one guy," Washington said. "They've got to worry about both guys blitzing, myself and LaVar."

"Any package that we have that's successful, we always want to make sure we always have it in the game plan," defensive end Renaldo Wynn said. "So we'll definitely use it a little bit this week."

Injuries to the defensive line could also result in more use of the 3-4 against the Giants. Cornelius Griffin, the anchor of the line, and Salave'a are not expected to practice much because of injuries, though they should play, while reserves Aki Jones (hamstring) and Cedric Killings (ankle) missed the San Francisco game. Once Griffin left that game the Redskins leaned more heavily on the 3-4.

"We used it more in the second half, but we were short defensive linemen," Blache said. "That was part of it."

The coaches have said all season that work in practice and in meetings would dictate how they use Arrington on game days. Arrington said that merely playing again was a significant step, and he aims to remain in the lineup permanently.

"One thing [defensive coach] Gregg Williams always talks about is making sure that every player is prepared to play and knows what they are doing on the field," Wynn said. "And I think [Arrington] has done that, and I know he's going to continue to do that."

Linebacker LaVar Arrington, eyeing 49ers rookie quarterback Alex Smith, thrived in Sunday's 52-17 romp.