SANTA CLARA, Calif. (AP) -- Two are All-Pros. One was the runner-up for the AP Defensive Rookie of the Year. The other just received a new $44.5 million, six-year contract extension.
Patrick Willis, NaVorro Bowman, Aldon Smith and Ahmad Brooks might not only be the biggest reason behind the San Francisco 49ers' defensive success last season, they form a close-knit linebacker group that has quickly become the NFL's new elite unit.
Call them the Fearsome Foursome.
''I think they're the best tandem of 3-4 linebackers in the league,'' Green Bay Packers quarterback and NFL MVP Aaron Rodgers said this week.
He should know.
When the Packers host the 49ers in the regular-season opener for both teams Sunday, the quarterback's eyes will likely be locked into the linebackers more than any other group on the field.
Willis and Bowman, the two All-Pros, combined for 235 tackles, 20 pass deflections, four sacks and four forced fumbles last season. Smith set a franchise-rookie record with 14 sacks to go with two forced fumbles. Brooks, who signed a new deal over the summer that will carry him through the 2017 season, had seven sacks and a forced fumble.
With the linebackers causing chaos, the 49ers led the league in rushing defense (77.2 yards per game), tied with the Packers in takeaways (38) and finished second only to the Pittsburgh Steelers (14.2) in points allowed per game (14.3) en route to the NFC championship game last season.
''There are certainly high expectations,'' Willis said, ''knowing what we did last year.''
The success has also bred a friendly but fierce competition throughout training camp and preseason practice.
Brooks and Smith are so competitive on the outside they started a game about who is best, often yelling out ''left side'' and ''strong side'' after big plays, mimicking the catch phrase from a scene in the movie ''Remember the Titans.'' Even defensive ends Justin Smith and Ray McDonald have gotten in on the fun.
While the Smiths are often quieter and prefer to let their play do most of the talking, left-siders Brooks and McDonald can often be more rambunctious.
''There were guys that said, 'Left side! Strong side!''' Brooks said. ''One day last year Ray was like, 'Left side!' And I was like, 'Strong side!' It stuck with us.''
All four believe the playful antics have motivated the defense even more.
''It's not a rivalry, it's like a friendly competition,'' Aldon Smith said. ''We want to see who can get more than the other. And just get 'em period.''
The success also has created a bond that extends beyond the field.
Willis and Bowman are basically brothers. The two have pictures of each other and their families in each of their lockers, and Willis also is the godfather to Bowman's newborn twins.
Sometimes it's even hard to tell who is who between No. 52 (Willis) and No. 53 (Bowman) the way both move all over the field.
As roommates during training camp last year, the two learned more about each other and the similar obstacles they had to overcome on separate paths to NFL stardom.
Bowman, entering just his second season as a starter, lost his father, Hilliard, to a blood clot and his school coach and mentor, Nick Lynch, to a car accident while Bowman was at Penn State. Willis' younger brother, Detric, drowned at age 17 when Willis was at Mississippi.
''Me and Pat, we are very, very close,'' Bowman said. ''We think of ourselves as one of the best and we have to keep going out there and proving it every single Sunday.''
Willis and Bowman both credit Hall of Fame linebacker Mike Singletary - fired as 49ers coach after the second-to-last game in 2010 before Jim Harbaugh took over in January 2011 - for guidance early in their careers. The ''hard-nosed'' coach instilled a strong work ethic in both, always preaching, ''You're never good enough,'' Bowman said.
That philosophy has proven powerful as they've evolved into one of the league's best units.
And with Ray Lewis and many Baltimore Ravens veterans in the twilight of their careers, Willis and Co. are already drawing comparisons to that vaunted linebacker group in its prime.
San Francisco defense coordinator Vic Fangio believes the next step for his linebackers is to show the same poise and polish for more than one season. While he heaps high praise on his defensive leaders, he's not ready to anoint the Niners linebackers the new NFL standard, especially given his history.
Fangio was the linebackers coach for the ''Dome Patrol'' in New Orleans from 1986-1994. Hall of Famer Rickey Jackson along with Sam Mills, Vaughan Johnson and Pat Swilling headlined that Saints squad.
The foursome combined for 18 Pro Bowls over seven seasons. In 1992, all four made the Pro Bowl.
''I get asked a lot, how do they compare to the four guys we had in New Orleans?'' Fangio said. ''Those four guys started for us in New Orleans for seven straight years together. Hopefully, we can have a run like that here and once we start doing that, two, three, four years, maybe I'll have a better answer to that question.''
NOTES: RB Brandon Jacobs (left knee) and WR/returner Ted Ginn Jr. (right ankle) did not participate in practice for the second straight day. Harbaugh has been noncommittal about whether either would play. ... 49ers offensive coordinator Greg Roman also opened the possibility that backup QB Colin Kaepernick could spell Smith at times to run the wildcat formation. ''I think Kap gives you the flexibility to be able to talk about that and feel good about it and plan for it,'' Roman said. ''I think it's just good change of pace and makes the defense prepare for something different. So, it's definitely a possibility.''
AP Sports Writer Janie McCauley contributed to this story.
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