SANTA CLARA -- Two players poised to emerge from the shadows say they've been in the dark about why they've been sitting out for the 49ers.

Receiver A.J. Jenkins and running back LaMichael James -- the team's top two draft picks in April -- are still waiting to make their NFL debuts. That could change Sunday against the St. Louis Rams in the wake of season-ending injuries to receiver Kyle Williams and running back Kendall Hunter.

Why hasn't Jenkins played?

"You have to ask Jim Harbaugh. I don't know,'' the receiver said.

And James?

"I have no idea," the running back said. "That's up to the coaches."

Harbaugh, as is his custom, said little when asked. He has not revealed anything this week about how he plans to replace Williams and Hunter on the game-day roster, saying only that some of the players who had been inactive could get an opportunity against the Rams.

Jenkins and James are the only two healthy players among the first 72 rookie draft picks who have yet to play an NFL game.

The only other top pick still waiting to hit the field is Pittsburgh Steelers guard David DeCastro (No. 24 overall out of Stanford), who sustained a knee injury during training camp and wasn't added to the Steelers' active roster until this week.

Neither Jenkins nor James said he has been told specifically what it would take to crack the roster. So, in the meantime, they're looking for ways to make their case.

Jenkins has spent time working on kickoff and punt returns -- skills that could be useful as the team looks for special teams depth after Williams' season-ending ACL tear.

"I'm trying to make my resume as long as it can be." said Jenkins, whom the 49ers drafted 30th overall. .

Jenkins' short-area quickness makes him a candidate to inherit some of Williams' responsibilities as a slot receiver, but the rookie said he's not over-thinking where he might fit in.

James, drafted 61st, led the nation with 150.4 rushing yards per game while at Oregon a year ago. This year, his rushing total is holding steady at zero. Beyond the injury to Hunter (torn Achilles), the rookie's opportunity for playing time might have gotten a boost with the change at quarterback.

James and Colin Kaepnerick showed some on-field chemistry during training camp.

"Me and Kap are really close," James said. "I think he's an athletic quarterback. Obviously when he has the ball, he makes plays. If I get the opportunity to play with him, I think it'd be fun."

After 11 games, James has grown accustomed to such mystery. Asked when he might get word as to whether he'd be playing this week, he smiled.

"Sunday, maybe," he said. "Probably Sunday during the game."

  • Defensive lineman Demarcus Dobbs was arrested early Friday morning on suspicion of driving under the influence and possession of marijuana, the California Highway Patrol said.

    CHP Officer D.J. Sarabia said that Dobbs was involved in a single-car accident in which he hit a chain-link fence and a bush but didn't sustain any injuries. He was arrested at 3:45 a.m. in Santa Clara, where the team trains.

    The arrest came on the 25th birthday for Dobbs, one of the 49ers' top special teams players. The 49ers released a statement Friday afternoon saying Dobbs wouldn't travel with the team Friday to St. Louis.

  • Getting a new deal for All-Pro linebacker NaVorrro Bowman required some teamwork, according to Comcast SportsNet Bay Area.

    The network said tight end Vernon Davis, cornerback Carlos Rodgers and defensive lineman Ray McDonald restructured their own contracts to give the 49ers enough salary cap room to accommodate Bowman's $7.5 million signing bonus.

    CSNBA noted that the overall framework for the other players' deals did not change. Davis' contract still averages $7.35 million through 2015, Rogers' average salary is $7.325 million through 2015 and McDonald's deal averages $4.02 million through 2015.

    That means the 49ers are $1.442 million under the league's salary cap.

  • The 49ers promoted practice squad linebacker Michael Wilhoite, 25, to the active roster and signed him to a two-year contract. Wilhoite (6-0, 240) was once a three-year captain at Washburn University (Kansas).

    The spot could have been used to sign a replacement kicker for ailing David Akers (pelvis). The team tried out veterans Billy Cundiff and Nate Kaeding, but Akers held up well during the week of practice.

    Asked about his emergency kicker, Harbaugh cracked: "(Punter) Andy Lee or (defensive lineman) Isaac Sopoaga."

  • With Williams (torn ACL) out for the season, Harbaugh said his new emergency quarterback is receiver/returner Ted Ginn Jr.

  • To replace Wilhoite on the practice squad, the 49ers re-signed safety Eddie Whitley, who had been released from the practice squad earlier in the week.

    The Associated Press contributed to this report.