Oakland Raiders starting C Stefen Wisniewski hasn’t practiced or played since injuring a calf in the exhibition opener against Dallas, and he’s in serious jeopardy of missing Saturday's game against Detroit.

Wisniewski missed the entire offseason program while recovering from shoulder surgery.

He has changed positions, moving from left guard to center, and is also learning a new offense and blocking scheme. Raiders coach Dennis Allen is concerned about the amount of time he has missed in camp.

“He needs to get the reps,” Allen said after practice Tuesday. “You don’t just show up and play, so every day he’s not out here he’s a little bit farther behind. He’s been keeping up mentally, as far as taking the mental reps and in the meetings, but it’s hard to replace those physical reps you get here and in games.”

Alex Parsons, who spent the past two seasons on the practice squad, filled in for Wisniewski during the offseason and has replaced him again in training camp.

“He’s done well,” Allen said of Parsons. “As a matter of fact, he was competing the whole time, and we were impressed with what we’ve seen out of him. Again, we’ve got a next man up philosophy. If Wiz is ready to go, great. If he’s not, then it’s next man up and Alex will go in there and play.”

Allen has no specific deadline for when Wisniewski needs to return to practice to be ready to start in the Sept. 10 opener. But he hinted that Wisniewski can’t miss too much more time.

Streater gets the starting nod: With Denarius Moore (hamstring) and Jacoby Ford (foot) sidelined, undrafted rookie WR Rod Streater will make his first NFL start Saturday against Detroit, Allen said. Streater has a team-best 13 catches for 109 yards.

“He can play with the best of them,” QB Carson Palmer said. “He’s everything you want in a young guy attitude-wise. He studies, understands the game. Coming into camp he had a very good feel for the game.”

Back in action: TE Brandon Myers practiced full-go for the first time since suffering a shoulder injury in practice just days before the exhibition opener against Dallas. Before Myers was hurt, Allen said he had taken the lead in his battle for the starting job with Richard Gordon and David Ausberry.

“It was frustrating,” Myers said. “It’s just a part of football. Now that I’m back, I just have to keep grinding and gain the trust of the quarterbacks and coaches. That’s what I’m trying to do.”

Getting serious: The Raiders, in many ways, are preparing for Saturday’s exhibition game against Detroit as if it were a regular-season game. The practice schedule has changed, starting at 11:05 a.m. and media access is now limited to the first 30 minutes.

“It’s more of a dress rehearsal, kind of taking the guys through how we’re going to go about game planning for a week all the way up until game day,” Allen said. “And we’ve got a little bit more in from a game planning standpoint this week than we normally do.”

Extra points: Ford continued to wear a walking boot on his sprained left foot. DT Richard Seymour, who has been nursing a sore knee during camp, missed practice again. LB Aaron Curry (knees), DT Jamie Cumbie (foot), OT Ed Wang (shoulder), OT Zach Hurd (head) and FB Rashawn Jackson (hip) were also sidelined. FS Michael Huff, who had been away from the team since Friday for the birth of his daughter, returned to practice. Backup QB Matt Leinart (lacerated right index finger) practiced and, according to Allen, should play Saturday.

Follow Raiders reporter Eric Gilmore on Twitter @CBSSportsNFLOAK.