NAPA, Calif. -- The Oakland Raiders will be without projected starting cornerback Chris Johnson for their preseason game against the 49ers on Saturday night and might also play without center Samson Satele.
As if that wasn't enough, wide receiver Louis Murphy will be sidelined indefinitely and likely miss the team's regular-season opener after undergoing a medical procedure.
With running back Darren McFadden already out with a fractured orbital bone, the Raiders are spending more time in the trainer's room than on the field.
"I told you I'm going to be very cautious with our football team," coach Hue Jackson said. "I don't bat an eye at those things when a guy goes down or a guy's out of here. I don't like it for our players, but you can't worry about that."
Jackson revealed that Johnson underwent a medical procedure that will keep him sidelined against San Francisco. Jackson declined to discuss specifics of the procedure but added that he expects Johnson to be back in time for the Raiders' regular-season opener at Denver on Sept. 12.
"Chris will be back here very shortly," Jackson said. "I'm not going to go into detail exactly what it is, but we had to have some things cleaned up with him, for him, and I think he'll be back and on the mend and ready to play."
Johnson had been working at left cornerback almost exclusively with Oakland's starters but left halfway through Sunday's practice and hasn't been back on the field since.
The Raiders' secondary has been a focal point during training camp ever since Pro Bowl cornerback Nnamdi Asomugha signed with Philadelphia as a free agent.
Rookie DeMarcus Van Dyke, the team's third-round draft pick who had a rough time in his NFL debut trying to handle Arizona's Larry Fitzgerald, replaced Johnson in practice Wednesday. The Raiders also have tried Walter McFadden at the position.
"It's an opportunity to show out, to show the team that I can play," Van Dyke said. "And this is an opportunity to show Coach Hue that I'm ready to play. I've improved a lot, and every day I try to get better at different things."
The loss of Johnson is another blow for Oakland's secondary.
Backup safeties Hiram Eugene (dislocated hip) and Zac Etheridge (knee) were both injured in the preseason loss to the Cardinals, forcing the Raiders to sign Josh Bullocks and Matt Giordano earlier this week as insurance.
The situation with the offensive line could get just as tricky if Satele is out for any length of time.
Satele, who had been taking most of the reps with Oakland's first team offense, left practice early then limped cautiously away from the team's training camp facilities.
"I'm good," Satele said before getting into a van driven by a team employee to be taken to a hospital for X-rays.
Jackson again refused to say how Satele got hurt but didn't think the injury was too serious.
"Nothing major, didn't get rolled on or nothing," Jackson said. "(He) just started feeling a little discomfort and we decided to get him out. Just didn't feel some strength in some areas. I really believe he's OK and he'll be fine. We'll do all the precautionary things that you need to do to make sure our players are OK."
That meant another position change for rookie Stefen Wisniewski, who had been lining up at left guard after originally being drafted to be Oakland's center. Wisniewski has played both positions in training camp but was at left guard only in the exhibition opener.
Additionally, only two days after Murphy told reporters that he's been slowed by a sore groin and hamstring Jackson said the third-year wide receiver may not be back until after the Raiders' opener in Denver.
"Murphy had a kind of procedure also," Jackson said, again declining to discuss details. "Murphy's was a little bit more extensive than Chris, so Murph might be out a little longer than C.J."