"Seattle running back Marshawn Lynch, acquired in an Oct. 5 trade, took a crash course in his new offense -- with an emphasis on crash.

The 215-pound running back even took aim at Seattle coach Pete Carroll last week when, in a spirited practice session, Carroll lined up at middle linebacker during a goal-line drill.

"I ran him over," the former Cal star said. "I gave him a stiff arm he'll remember for a while."

Lynch and his coach were just goofing around, but it will be all business Sunday when the Seahawks face the 49ers at Candlestick Park. Seattle can eliminate the 49ers from the NFC West race with a victory.

Unlike veteran running back Brian Westbrook, who eased into action with the 49ers, Lynch jumped into action in Seattle. Acquired from Buffalo, Lynch was in the starting lineup 12 days later on Oct. 17.

49ers coaches expressed repeated reservations about Westbrook being ready to handle pass-protection assignments.

Seattle had no such concerns with Lynch.

"It has not been a difficulty at all," Carroll said in a conference call with Bay Area reporters. "He's a very bright player, gets it, studies really hard. That really hasn't been an issue at all."

He added: "Marshawn has never had any problem with anything. Obviously, the first week we were careful with him, and the second week were kind of growing with him. But from that point on, we haven't hesitated at all.""