ST. LOUIS — The Rams will have a new face in the lineup plus a couple of familiar ones back in action Sunday when the Miami Dolphins visit the Edward Jones Dome.

Rookie David Vobora will make his first start, taking over for Will Witherspoon at middle linebacker. Witherspoon is nursing injuries to both shoulders and will be used only on third downs and in the 2-minute defense, coach Jim Haslett said.

Orlando Pace will be back at left tackle after sitting out last week's game with a knee ligament injury, and running back Steven Jackson is expected to play after missing four of the past five games with a strained thigh.

Jackson practiced all week, stepping up the pace each day. After Friday's practice, Haslett still was being cautious about Jackson's status. "I thought he got better as the week went on," Haslett said. "I'll talk to him and we'll make a decision by the game."

But team officials said Jackson will suit up and probably will start. Jackson conceded that he'll have to guard against being tentative in his return.

"Yeah, that's the next thing," he said. "Although I'm practicing, I still want to run through some arm tackles, drag some guys around. The leg strength is there. ". . . As the weeks go by, the confidence will come and the doubt in my mind will leave as well."

Vobora, a 6-foot-1, 238-pound University of Idaho product, was the last pick in April's draft, earning him the distinction of "Mr. Irrelevant." He was activated from the practice squad Nov. 4 and has played in the past three games, mostly on special teams.

He'll be the first "Mr. Irrelevant" to start a game in his rookie season since 1994, when Marty Moore made four starts at linebacker for the New England Patriots.

"It's been a dream come true to get to this point, but there's no complacency," Vobora said. "I always want more, and this is a good opportunity to get in and contribute and show, 'Hey, this is what I can do; this is what I bring to the table.'"

It's an opportunity that triggers a bit of anxiety, too, he acknowledged. "I have 10 other guys depending on me, so I want to make sure that I'm in the right spots," he said. "And when the play's there to make, make it."

Witherspoon, who had started all 43 games since signing a free-agent deal with the Rams in 2006, declined to speak with reporters Friday.

Auditions begin

With the Rams eliminated from playoff contention, Haslett plans over the final five games to audition several players who haven't participated much on Sundays.

"We're going to find out what other guys can do," he said. "Anybody that's dressed, we're going to try to take a look at them. ... This will give us a chance to see them live, with the bullets flying."

Veteran wide receiver Torry Holt, whose role has been reduced this season with the emergence of youngsters Donnie Avery, Keenan Burton and Derek Stanley, endorsed that approach.

"I think it's great for the young players, and I think it's good for this football team and for this organization as they move forward and see what their plans are going to be here in the future," he said. "They have to take a look and see who's going to be here, see who's going to help them out. "&

"I'm looking forward to having the opportunity to watch some of them play."