The 6-foot-2, 250-pound Banta-Cain, who won Super Bowl rings in his first two years with New England, had career highs of 40 tackles and 5 1/2 sacks last season while playing in all 16 games for the Patriots. He became a starter when Junior Seau was hurt in November, but New England replaced him with free-agent linebacker Adalius Thomas on Saturday.

Banta-Cain is the fifth free agent in five days to join the 49ers, whose spending spree began with an eight-year, $80 million deal for cornerback Nate Clements. San Francisco also signed safety Michael Lewis and nose tackle Aubrayo Franklin to bolster a defense that yielded an NFL-worst 412 points last season.

The 49ers also agreed to terms with former University of Hawaii receiver Ashley Lelie yesterday after releasing No. 1 pass-catcher Antonio Bryant four days earlier.

Banta-Cain could play a prominent role in San Francisco's revamped 3-4 defense as an outside linebacker and pass-rusher.

Banta-Cain said he got an offer from St. Louis earlier during his free-agent tour, but canceled a trip to Pittsburgh after agreeing to return home to Silicon Valley.

"I just felt like it was the right fit," Banta-Cain said. "The scheme that they run here, coming from a very similar scheme, and seeing that the defense could use some help, it just seemed like I could come here and make a big impact. ... It looks like they could use some help in the pass-rush department, getting to the quarterback, and that's sort of my specialty."

Banta-Cain grew up in Mountain View, Calif., just a few minutes from the 49ers' training complex in Santa Clara, before playing defensive end at California. His parents and most of his extended family still resides in the Bay Area, a key factor in his decision.