LAKE FOREST, Ill. -- Stopping Frank Gore and the San Francisco 49ers running attack Monday night is the No. 1 priority for a Chicago Bears defense that has surrendered 100-yard rushing performances in each of the last two games to Tennessee's Chris Johnson and Houston's Arian Foster.

The Niners will try to run the ball against the Bears' fourth-ranked rushing defense (92.3), that much is certain. San Francisco is the top-rated rushing offense in the league with 170.2 yards per game on the ground for an average of 5.6 yards per carry. The 49ers also lead the NFL in overall rushing yards (1,532) and carries of 10-or-more yards (52) and are second in the league with 83 rushing first downs.

At the center of it all is Gore, the NFL's eighth-leading runner with 753 yards and five touchdowns. Since 2005, Gore leads the league with 32 100-yard rushing games.

"He's physical, wow," Bears defensive coordinator Rod Marinelli said. "He's downhill, one cut, and every yard he's fighting for. He twists and turns, he fights, this guy is never down. He's never down."


The Niners' commitment to the run also allows for plenty of opportunities to play-action pass down the field. Starting quarterback Alex Smith, who has completed a league-high 70.4 percent of his passes, has a multitude of offensive weapons at his disposal that can stretch the field and exploit a defense that is solely focused on Gore.

But when San Francisco runs the ball effectively, it usually wins. The 49ers are 25-7 when Gore goes over 100 yards rushing.

"It all starts with the run," Marinelli said. "They set you up with the run, suck you in with the run and then throw the ball. It's very similar to what we saw last week. They take the rush off you a little bit. The tight end is like a receiver. They also have Michael Crabtree, Randy Moss, Mario Manningham, a bunch of fast guys. But everything is predicated really on establishing the run game. They do a great job with personnel. They have great packages with a lot of big guys, so you need to work hard at practice each day to make sure you are ready for all those looks."