SANTA CLARA (AP) — With a full offseason to work with one of the NFL’s most fearsome units, Vic Fangio sees no limit to what the San Francisco 49ers can achieve on defense this season.

That unit accomplished plenty last year while pushing the Niners to their first winning season in eight years. But with all 11 starters returning on the league’s fourth-ranked defense, it looks to be even better in 2012.

Fangio has guided several top-notch defenses during his 26 years coaching in the NFL, and San Francisco’s defensive coordinator says this could be his best yet.

“I suppose you could say potentially we should be as good or better,” Fangio said Wednesday, the midpoint of a three-day minicamp. “We have good players and our guys enjoy playing with each other. They grew into playing with each other last year, playing off of each other. We would expect that to continue and take it to a higher level.”

After years of flirting with success, San Francisco’s defense reached the top level last season in Fangio’s first year with the team. And that came without the benefit of an offseason program for Fangio to implement a new system because of the NFL lockout.

The 49ers prospered defensively anyway and were considered one of the league’s elite units by the time San Francisco had completed a surprise run to the NFC Championship game, where it lost in overtime to the eventual Super Bowl champion New York Giants.

The Niners are envisioning great things ahead after an entire offseason program to absorb Fangio’s 3-4 defensive scheme and the new wrinkles he’s adding with the additional preparation time.

“It’s really just enabled us to pick up where we left off last year, reinsert our defense to brush that off, and then polish off what we had inserted to even a finer level of execution,” Fangio said. “And we’ve added a thing or two here and there that gives us something new to work on.”

The 49ers don’t envision many changes to a unit that last season led the NFL in rushing defense and takeaways, was second in points allowed and ranked in the top 10 in 10 defensive categories.

San Francisco is rock-solid across the board at virtually every defensive position with star linebacker Patrick Willis, tackle Justin Smith, cornerback Carlos Rogers and safety Dashon Goldson all selected for the Pro Bowl last season. Linebacker NaVorro Bowman joined Willis and Smith on the All-Pro first team.

But one thing the team’s working on this spring is the addition of second-year pro Aldon Smith to the starting lineup at outside linebacker in place of incumbent Parys Haralson.

Smith, San Francisco’s first-round draft pick in 2011, made a huge impact on passing downs last season, setting a franchise record for a rookie with a team-leading 14 sacks.

Haralson is strong against the run and started every game last year with the base defense. But Smith got onto the field for almost 52 percent of San Francisco’s defensive plays, and the 49ers intend for that number to increase significantly this season.

“When you have a player of his ability, you’ve got to do anything and everything you can to get him on the field more,” Fangio said. “I was very happy and pleased with what we got out of him last year. We expect him to become more of a full-time player this year.”

The 49ers have a lot of expectations for their defense this year. But then, so does everybody else.

The Niners won’t sneak up on anybody this year after the way their defense emerged last season.

“People know who we are, considering what happened last year,” Aldon Smith said. “But we still have the same mentality. We’re hungry and we’re working hard every day to get better. We’ve got a lot of guys who work hard and do their job. As long as we keep getting better, the sky’s the limit for us.”