SANTA CLARA, Calif. (AP) - Just when San Francisco's offensive line seems back on track carrying a little swagger, here comes the ferocious Ndamukong Suh and Detroit's punishing pass rush.

He's big. He talks a big game. He backs it up, too. And Suh isn't the only one. The Lions are loaded on their front line.

Ask Suh, and Alex Smith better watch out if his O-line doesn't bring its best stuff Sunday. He will hit the quarterback, and not just once. This Lions' unit is competitive, with one mantra: ``meet you at the quarterback.''

The film says it all,'' 49ers offensive coordinator Greg Roman said Thursday.Those aren't empty words.''

San Francisco (4-1) didn't allow a sack in its 48-3 rout of Tampa Bay on Sunday, while the unbeaten Lions (5-0) had three sacks of Jay Cutler on Monday night - but that number just hints at the amount of constant pressure Cutler faced. Chicago committed nine false start penalties in the 24-13 loss.

For a San Francisco offensive line that faced harsh criticism only a few weeks ago, things are suddenly clicking. Smith has time to make the right decisions and not fear for his life. He has stayed upright. All that after the 2005 No. 1 overall draft pick took pounding after pounding during the early stretch of the season - sacked 14 times so far.

Suh hopes there's more of that Sunday at Ford Field. He is one of the most confident guys in a game full of them. The reigning Defensive Rookie of the Year, and the only rookie All-Pro in 2010, has been fined for roughing up quarterbacks and doesn't apologize for it. He has two sacks this season after recording 10 as a rookie.

If you're not going to protect me from your quarterback, I'm going to continue to hit him,'' he said on a conference call with Bay Area reporters.It's not necessarily me putting fear of life - I want you to be scared of me - it's the fear that if you don't take care of business and study and come up with a great plan, I'm going to hit him. The other eight, nine guys I play next to are going to hit him as well.''

Smith has been safe lately. He trusts the men paid to protect him, even if they got off to a rough start.

``The offensive line is playing great,'' he said.

Most of San Francisco's front five say there are a few simple things making the difference: attention to detail, improved technique and just a better overall understanding of the offense.

We're two weeks more into the offensive system,'' right guard Adam Snyder said.Guys are getting a better understanding of where we're at as far as the game-planning.''

Coach Jim Harbaugh also made a key change from Chilo Rachal to Snyder starting the past two games, and that move has paid off.

While Suh has his words, Harbaugh has been using his own unique message around team headquarters this week. He reminds his players that winning can make you ``soft.''

We've seen no evidence of that,'' he said.We will be quick and on alert for any signs or evidence. There's a guy that walks around by the name of Frederick P. Soft. Freddy Soft's about a four-inch guy that sits on your shoulder, talks right into your ears. If we see or hear any evidence of him being in the premises we will act quickly and decisively and get him out of here.''

Defensive coordinator Vic Fangio is all for whatever ``fun'' ways Harbaugh finds to motivate.

Left tackle Joe Staley did his part to get his linemates going.

The early struggles prompted the frustrated veteran to publicly say the offensive line doesn't ``suck'' ahead of the 49ers' 24-23 comeback road win over the Eagles on Oct. 2.

My emotions got the best of me there,'' Staley later said of his language.I felt like I had to stick up for my guys. I just know how hard we work.''

The matchup in Detroit on Sunday will demand that everybody is on task with each snap. Crowd noise contributed to all those false starts by the Bears. Not to mention Suh's massive presence.

Staley doesn't consider the focus of the Lions' line - getting to the QB - any different from other teams.

``It's going to be a great fight Sunday,'' Staley said.

While left guard Mike Iupati is nursing a sore right knee, he said Thursday he's good to go and he took part in practice. If needed, Rachal could fill in at one of the guard spots.

Snyder is most likely to be face to face with Suh all day. He typically lines up against the right guard, and anything goes when dealing with Suh.

``I'll consider myself a dirty player when my mom calls me a dirty player,'' Suh said during training camp.

Snyder, among the lightest guards in the league at 295 pounds, is feeling stronger and quicker since losing 25 pounds in the offseason primarily by improving his diet. Smith has been sacked only three times in Snyder's two starts, compared to 11 with Rachal in the lineup.

Lions coach Jim Schwartz used nine different players on the defensive line against Chicago to keep everybody fresh and effective. That approach is working well.

Ndamukong Suh doesn't stand alone,'' Schwartz said of his powerful D-line.It's the heart and soul of our team and the strength of our team. It was last year and it is again this year.''

First-round draft pick defensive tackle Nick Fairley is coming off his debut after missing two months following foot surgery - making him the ninth active defensive lineman. Yet not many outside of Detroit have heard of these guys, like defensive end Willie Young. He came up with a late-game sack. Another backup defensive end, Lawrence Jackson, also had a sack.

You have to study all those guys,'' Roman said.They're going to roll them in and keep them fresh.''

AP Sports Writer Larry Lage in Detroit contributed to this story.