SANTA CLARA -- Where has the 49ers' pass rush gone?It seems the opposition has been quick to do something about slowing down the 49ers' four-man pass rush through the first six games of the season.The 49ers' sacks and interceptions are down -- cut in half from a year ago. That's the bad news for the 49ers.But the 49ers' pass defense is also better than a year ago, as they have also cut in half the number of big plays allowed this season.Defensive coordinator Vic Fangio does not seem concerned with the pass rush. The reason, he said, is because he has seen quicker passes and the opposition is keeping in more backs and tight ends to serve in pass protection."At times, they'll be chipping us, keeping extra guys in, or throwing it quicker," Fangio said. "I think it (the 49ers' pass rush) is on their mind. I think that plays into the pass defense, which is what we're all concerned about here. When they do that, they limit themselves also a little bit."The numbers seem to support Fangio.If quarterbacks have all day to throw, then why have they connected on only 11 passes of 20 yards or more? The 49ers have given up only three pass plays of 30-plus yards, and one came on a screen pass to a running back.A year ago through six games, the 49ers gave up 22 pass plays of 20 yards or more, including eight plays of 30-plus yards."Now, we didn't have a good rush on one of the passes they (New York Giants) completed for good yardage," Fangio said. "But that's going to happen some. But I dont see our pass rush as being an issue right now."The 49ers must be doing something right with their pass defense. They have already faced Aaron Rodgers, Matthew Stafford and Eli Manning, and the 49ers rank second-best in the league in passing yards allowed."Pass rush is a part of pass defense," Fangio said. "So although we don't have the sack numbers, which a lot of people want to sink their teeth into, fantasy players want to sink their teeth into sacks. That's not the only measure of a good pass rush. And right now to this point, I haven't seen pass rush as being a weakness for us."The 49ers have surrendered only 1,162 passing yards (193.7 per game), compared to 1,689 yards (281.5 per game) at this same point a year ago. On third downs, the 49ers have been the best in the league, allowing the opposition to convert on just 35 percent of their opportunities.Conversely, the 49ers rank 26th in the NFL in sacks per opponent pass play. They are also tied for 26th with nine sacks in six games. Aldon Smith leads the 49ers with 4.5 sacks. Ahmad Brooks has three sacks. They have intercepted four passes.A year ago, the 49ers had 17 sacks and eight interceptions through six games.The opponent passer rating is nearly identical. It was 77.7 last season at this time, and it's currently 77.8.It goes to reason that opposing offenses are trying to slow down the 49ers' pass rush, but it comes at a price. Shorter pass routes are going to cut down on sacks and interceptions. In doing so, teams are limiting their own ability to hit big plays down the field.Outside linebacker Aldon Smith, who recorded 14 sacks as a rookie, leads the 49ers with 4.5 sacks through six games. He also has 14 hits on the quarter, according to statistics kept by the team's coaching staff.Justin Smith, who had 7.5 sacks, does not have any while facing regular double-teams. But Justin Smith leads the 49ers with 19 hits on the quarterback.Outside linebacker Ahmad Brooks has three sacks and 17 quarterback hits, while defensive tackle Ray McDonald has a half-sack and 18 hits on the quarterback.The 49ers have not felt compelled to blitz more than usual because the ball is coming out quickly and it would only serve to weaken the coverage. Cornerback Carlos Rogers has the only sack by a non-traditional pass-rusher. Inside linebackers Patrick Willis and NaVorro Bowman have combined for no sacks and just four quarterback hits.And even though the 49ers will be facing a rookie quarterback Thursday night against the Seattle Seahawks, it does not mean Fangio will dial up a wide array of blitzes.Last November, the 49ers did not send more than four pass rushers -- and many times rushed only three -- in a 23-7 victory over the Arizona Cardinals. Fangio later explained that sometimes against young quarterbacks, such as Arizona's John Skelton, it's best to try to confuse them with coverages in the secondary, rather than force them to get rid of the ball quickly on hot reads against a steady diet of blitzes.Seattle's rookie quarterback, Russell Wilson, will make his seventh NFL start on Sunday. He said he welcomes the challenge of blitzes."The main thing is just getting rid of the ball quickly," Wilson said Tuesday on a conference call with Bay Area reporters. "Once they do pressure, there's a lot of green grass behind it, too. If you can capitalize on those blitzes, it gives you opportunities to make big plays down the field."