"Today in rehab, the leg's still tight, the groin's still tight," said Jackson, who was hurt Sunday during a 30-16 victory over the Washington Redskins. "So it's just one of those injuries where just time is what's really going to heal the injury. The most I can do now is still mentally prepare myself as if I'm going to go Sunday."
The Rams (1-2) will play the Seattle Seahawks (2-1) at home Sunday. Seattle has beaten St. Louis in the last 10 meetings.
St. Louis coach Steve Spagnuolo acknowledged Jackson's "still a little bit sore, so it's day-to-day. We'll wait and see what happens."
Jackson admitted he didn't know if he would be able to go.
"I'm just going to continue to rehab and continue to be smart with it," Jackson said. "I think that's the biggest thing is to be smart with the injury."
If Jackson is unable to play, backup Kenneth Darby will likely get his first NFL start. Darby has been an infrequent contributor since signing with the Rams in 2008, but scored the go-ahead touchdown against the Redskins on a 12-yard run.
Keith Toston, the other backup running back, played with a sprained shoulder most of the way against the Redskins Chauncey Washington, a running back signed off the New York Jets practice squad Tuesday night, could be pressed into duty.
Pat Shurmer, the Rams' offensive coordinator, said his game plan will involve all possible players if Jackson does not play.
"We try to put the scheme together with the idea that our best players are going to be in there," Shurmer said. "Obviously, Steven being in the game is of some importance."
Darby had a career-high 14 carries and averaged 3.5 yards per attempt in gaining 49 yards in relief of Jackson.
"I thought he did a terrific job," Shurmer said of Darby. "The key to a role player is being able to come in and execute having had very few reps through the week."
Jackson did not sound like a player who will be playing Sunday but he did not rule it out.
"That's definitely what we're going to come down to this weekend is one, seeing if I can get through the game, and weighing this is a huge game for us," Jackson said. "This is Seattle at home where we're only one game back in our division. Although it's early in the season, this game has a lot that come out victorious, that does a lot for us in our season. ... I will be there early Sunday seeing if I can run and cut and seeing if I can go out there and give my team a lift."