Running back Steven Jackson was listed as questionable Friday on the St. Louis Rams injury report. Under NFL guidelines, that means his chances of playing in Sunday’s home game vs. the Seahawks are 50-50.

Jackson, who has been experiencing back spasms, missed a third straight day of practice Friday, although he did some individual work with the trainers on the sideline.

Coach Steve Spagnuolo said he plans to talk with Jackson, the NFL’s No. 2 rusher, on Saturday morning and make a decision — although Spagnuolo hinted that he could wait until after Sunday’s pregame warmups.

“I trust Steven and what he can tell me,” Spagnuolo said. “The competitive juices come out. But I think he’s been in the league long enough that he knows he doesn’t want to hurt the team, yet he wants to be out there to help the team.”

The Rams potentially could be without four other offensive starters. Quarterback Marc Bulger (left) is out, and although tackle Jason Smith (concussion) was listed as doubtful, Spagnuolo said, “We’re not going to have him for Sunday. Guard Richie Incognito (foot) and fullback Mike Karney (neck) are questionable.