GLENDALE, Ariz. – The 49ers' 2011 defense kept teams out of the end zone, suffocated running games and sent quarterbacks sprawling – cleats-over-helmet – onto their backs.

But it had one soft spot.

The unit gave up 12 pass plays of 40 or more yards – fifth-worst in the league – during the regular season, then allowed two more such plays to Drew Brees and the Saints in the final five minutes of the divisional playoff game.

This season, the 49ers have allowed just two pass plays of 40 or more yards, a 49-yard reception by Green Bay's James Jones in Week 1 and a screen play that Detroit running back Joique Bell turned into a 50-yard gain in Week 2.

The improvement in that category goes a long way in explaining why the 49ers enter tonight's game against wide receiver Larry Fitzgerald and the Cardinals with the top-ranked pass defense in the league. They are allowing 173.4 passing yards a game, nearly 60 fewer yards than they averaged last season.

"It's just a product of our guys being more comfortable in the system this year," defensive coordinator Vic Fangio said. "Playing that little bit better that I told you they would play just by being in the system."

Three of the 12 big pass plays against the 49ers last season came in one game, the team's Dec. 11 loss to Arizona. The 49ers knocked starting quarterback Kevin Kolb out of the game, intercepted his replacement, John Skelton, twice and forced him to fumble. They held the Cardinals to 55 rushing yards.

But each of the three long passes either resulted in a touchdown or put the Cardinals deep in the red zone, and San Francisco fell 21-19. On one play – a 46-yard touchdown to Fitzgerald – the receiver battled safety Dashon Goldson for the ball in the air, and when Fitzgerald descended with the ball, there was no one to stop him from running into the end zone.

That was the theme on the long pass plays last season. Most were short or intermediate throws that turned into big gains when the 49ers either missed a tackle or were too aggressive in going after the ball.

Goldson, however, is part of the group that has made an incremental, but noticeable, improvement from last season. He was awarded a game ball following the 49ers' Oct. 18 win over Seattle after intercepting a Russell Wilson pass and becoming a de facto fifth linebacker against Marshawn Lynch and Seattle's running game.

Fellow safety Donte Whitner noted that Fangio has given him and Goldson more freedom this season to trust their instincts and make coverage calls. That, coupled with the year's worth of experience in Fangio's system, has resulted in tighter coverage, he said.

"We watch a lot of film here during the week, and guys take film home with them," Whitner said. "So if we see something in the defense and feel like it would be better another way, (Fangio) trusts us to go ahead and change that in the secondary."

Goldson's game against the Seahawks wasn't perfect.

He was hit with a 15-yard unsportsmanlike conduct penalty for taunting Lynch, then was fined $7,875 last week for the same incident. Last year, the NFL fined him $25,000 for throwing punches at Cardinals wide receiver Early Doucet during the teams' first meeting.

Goldson acknowledged he needed to curb the trash talking but said he wouldn't stop being aggressive.

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