SANTA CLARA (AP) — Nobody represents the win-now mentality of the San Francisco 49ers more than Justin Smith. The All-Pro defensive tackle will tell you so himself.

The 49ers concluded their offseason workout program Thursday with Smith stressing the urgency he sees developing as the defending NFC West champions prepare for the 2012 season.

San Francisco has built a contender expected to challenge for the Super Bowl. Those hopes are built around players such as Smith, one of nine 49ers to earn Pro Bowl honors last season and a leader on a defense that returns all 11 starters.

Entering his 12th NFL season, Smith says he and the 49ers have a window of opportunity that doesn’t come around often. And many of those around him in the locker room feel the same way.

“The mindset I’ve kind of been spreading to the guys is, your team isn’t always going to be stacked, we’re not going to be able to keep this team together forever,” Smith said.

“So let’s go out and try to hammer this thing home,” Smith said. “You know, we’re not building, so let’s do it this year. It’s the goal of 31 other teams as well, so it’s going to be a tough one to achieve. But we feel like we’ve got the right team to do it.”

That’s quite a contrast to last year at this time, when the 49ers were coming off a string of eight consecutive seasons without a playoff berth and starting over again with a new coaching staff led by Jim Harbaugh, San Francisco’s fourth head coach in nine years.

Since then, the 49ers made a surprise run to the NFC Championship game, then loaded up during the offseason with free agents and draft picks to bolster the weak areas of their roster.

San Francisco’s offense - which finished 26th in the NFL rankings last year - has looked better during workouts this spring. That had flamboyant tight end Vernon Davis stating last week that the 49ers should be considered Super Bowl favorites this season.

Davis didn’t exactly back away from that comment in a group setting this week.

“I don’t want to sound too cocky, but I think we have the potential,” Davis said. “I think we have a lot of potential and I’m not wrong for saying that because of the talent we have. I can’t say that we’re going to win the Super Bowl. All I can say is that I strongly believe that we have the team to get to that point. It makes me excited because I know what we have going forward.”

San Francisco’s sturdy defense has produced a lot of the excitement after finishing fourth in the NFL rankings last year and leading the league in rushing defense and takeaways while finishing second in fewest points allowed.

That unit is anchored up front by Smith, who displayed his strength and versatility in the team’s 3-4 scheme last season by earning All-Pro first-team honors at defensive tackle while also earning All-Pro second-team honors at defensive end.

Smith will carry a streak of 171 consecutive starts into this season, which ranks third among all active NFL defenders and first among defensive linemen. Smith, who turns 33 in September, rarely misses a snap and shows no signs of slowing down after producing the best season of his career in 2011.

Smith’s approach and the way he takes care of his muscular 285-pound body have become examples for others.

“It always helps when your best players are your hardest workers,” 49ers defensive coordinator Vic Fangio said. “He definitely falls in that category. And it’s easy for young guys to follow suit. Justin stays on top of it, and he’s still here and playing at a high level. He gives us tremendous run play and pass rush, and his intangibles from his leadership and toughness are off the charts.”

Smith knows it won’t last forever and he has no interest in hanging on when he no longer can handle duty as an every-down player. But he doesn’t foresee that day coming for a while.

And after recording the first playoff victory of his career last season, Smith is eager to go farther with San Francisco.

“I figure I have three more good years in me, four more good years,” Smith said. “I’m figuring, ‘Let’s go.’ Time is of the essence for me. I think everybody feels the urgency and we’ve got the guys right now. And let’s not wait.”