Lamar Smith’s short stint as the Seattle Seahawks’ starting running back is over.

An MRI Monday revealed that Smith sustained a stress fracture in his lower left leg in the 17-9 victory over St. Louis Sunday.

Smith’s injury will keep him out at least a month, coach Dennis Erickson said.

In addition, the Seahawks have four starters - wide receiver Mike Pritchard (left knee), offensive tackle Walter Jones (right ankle sprain), guard Derrick Graham (pinched nerve, shoulder) and strong safety Bennie Blades (pinched nerve, neck) - who are questionable for Sunday’s home game against Oakland.

“We’ve just got to go,” Erickson said. “Everybody’s got injuries.”

Smith, a fourth-year player, who was the Seahawks’ third-round draft choice in 1994, is the team’s leading rusher after seven games with 280 yards on 60 carries, a 4.7 average, and one touchdown.

“He’s played well,” Erickson said. “Fortunately, we have some depth there.”

Smith became Erickson’s starting running back two games ago after former Pro Bowl selection Chris Warren was lost because of a pulled hamstring. Warren played Sunday in St. Louis, but Smith started and had 21 yards on eight carries.

With Smith out, the starting job will be given to either Warren or Steve Broussard, Erickson said.

“I haven’t decided yet,” Erickson said. “Obviously, you’re down to two backs now, so they’re going to share the time.”

If Pritchard is out, he will be replaced by Brian Blades or James McKnight. Grant Williams would be Jones’ replacement, Jay Bellamy would go in for Bennie Blades and Frank Beede would replace Graham.

The Seahawks have won four of their last five games, including two in a row. Their defense has given up three touchdowns the last five games, with nine interceptions and 14 sacks.

The big test this week is Napoleon Kaufman, who rushed for a club-record 227 yards in Oakland’s 28-25 victory over Denver.

“It was scary,” Erickson said of Kaufman’s performance.