SANTA CLARA -- A.J. Jenkins and LaMichael James, the 49ers' top two draft picks, remain on standby.Neither Jenkins nor James has stepped onto the field during the regular season. And even with season-ending injuries to receiver Kyle Williams and running back Kendall Hunter, there is no indication Jenkins and James will suddenly be asked to fill significant roles in the 49ers' offense.The 49ers' top three wide receivers are Michael Crabtree, Mario Manningham and Randy Moss. Receiver Ted Ginn, the return man, will also be among the 49ers' 46 active players.In order for Jenkins to find a regular role, he would have to be the team's slot receiver in three-receiver formations. Crabtree and Manningham are both capable of playing the slot. And both have done it quite well, according to Pro Football Focus.Crabtree has lined up in the slot 96 times, while Manningham has been there for 41 snaps. Among NFL players with at least 40 plays from the slot, Crabtree and Manningham rank second and third in average yards receiving on plays from the slot.In order for Jenkins to get regular playing time, he would somehow have to nudge out Moss in three-receiver sets. And that seems unlikely.Jenkins said he has learned all of the receiver positions on the outside and the slot. And he appears to be remaining patient for his opportunity."It's the first time in my life I've ever red-shirted," Jenkins said. "Right now, I'm going to use this time to learn my craft and everything, and learn from the vets. When my number is called, I'll be ready to go."A potential role for James is a little easier to envision, but it's certainly not a sure thing, either.With Colin Kaepernick as the starter, the 49ers run the zone-read play with greater frequency. It was one of the staples of the 49ers' offense when Hunter was on the field. Theoretically, Kaepernick and James could team up for that play with Hunter unavailable.After all, Kaepernick and James ran the play very effectively during the exhibition season."Kap ran this offense at Nevada, and I ran it at Oregon," James said. "He does a lot of reads, and I ran a lot of reads at Oregon. I think the chemistry was there, just working with him each and every day in practice. And I think it helped us out tremendously."However, Kaepernick and James have not practiced the play since the end of training camp."(It's) surprising, but I haven't," James said.The reason is because James has seen almost all of his practice time since the beginning of the regular season on the scout team. He is one of the players entrusted to run the opposition's plays in order to prepare the 49ers' defense for the upcoming game."I'm a competitor. I want to go out and play and compete," James said. "But I'm smart enough to know that I still have a lot to learn. This is the NFL. This is a complex offense. There are a lot of things I don't know."Another obstacle standing in the way of James making a contribution is special teams. For most of this season, the 49ers have activated three running backs. Anthony Dixon has been active for every game because he is a core special teams player.Brandon Jacobs, who now figures to be the backup running back, has played in only one game because he does not make a contribution on special-teams coverage units. To place James among the 49ers' 46 active players in Sunday's game means the 49ers would have two running backs in reserve who do not play on the coverage units.Both Jenkins and James are trying to make themselves more versatile -- and, thus, more valuable -- by remaining after practices to work on catching punts and returning kickoffs. James is listed on the 49ers' official depth chart as the backup to Ginn at both of those spots.