ST. LOUIS — The St. Louis Rams have struggled to stop the run all season. The test only gets harder today when they face Tennessee's Chris Johnson, the league's leading rusher.

The Rams rank 28th in run defense, allowing 146.2 yards per game. Over the last four games, all losses, St. Louis (1-11) has allowed an average of 6.8 yards per carry.

Johnson has 1,396 yards rushing through 12 games, including seven straight reaching 100 yards to tie the Titans' franchise record set by Earl Campbell when the team was the Houston Oilers.

St. Louis coach Steve Spagnuolo said Friday he has an idea on how to stop Johnson, who has helped Tennessee climb back into the playoff hunt. After beginning the season 0-6, the Titans are now 5-7.

"Get 12 guys on the field," Spagnuolo joked. "He's no different from anybody else. Defense is just playing downhill, filling gaps, getting off blocks and tackling the ball carrier. I mean, it's just that simple."

It hasn't been that simple for St. Louis. Even lesser-known players like Seattle's Justin Forsett (130 yards and two touchdowns) and Arizona's Tim Hightower (110 yards) have had their way with the Rams.

Rookie middle linebacker James Laurinaitis noted the defense has to keep after Johnson.

"He's never down," Laurinaitis said. "He's the most explosive guy we've faced. He's the biggest home run threat we've faced."

The key to stopping Johnson is remaining disciplined, defensive coordinator Ken Flajole said.

"More than anything, you can't get out of your gap against this guy," Flajole said. "Because he does have such good vision, he seems to find you when you're not where you're supposed to be."

Rams running back Steven Jackson is having a good year himself, trailing only Johnson with 1,120 yards. Jackson missed his ninth consecutive practice Friday with a balky back but is expected to play at Tennessee. He has topped the 100-yard mark 10 times this season.

Still, he's among Johnson's fans.

"Chris is having an unbelievable year," Jackson said. "He's having a year I can only dream of having one day. I'm a big fan of his. Not only is he a speedy guy, but he's willing to take a pounding. He runs bigger than what he actually is."