NAPA, Calif. (AP) - Raiders coach Dennis Allen's plans to have his team practice in pads were altered by a rash of injuries.

More than a dozen players were sidelined for Sunday morning's workout, including six projected starters on defense. That forced the team into a scramble mode just to get through practice.

Obviously (injuries) are a part of camp, part of the things you have to deal with,'' Allen said.But it is frustrating to not have guys that you're counting on to be out there on Sundays be able to go through practice. This is part of where we develop the foundation of the team that we're going to be.''

Khalif Barnes, Oakland's starting right tackle the past two seasons, moved inside to guard after Mike Brisiel was held out. Alex Barron, a reserve left tackle, switched sides to replace Barnes.

In the secondary, first-round pick D.J. Hayden and Chimdi Chekwa, both backups, took all the reps at cornerback with the first-team defense, while Mike Jenkins and Tracy Porter were held out. And Hayden, who hasn't played since suffering a near-fatal heart injury that required follow-up surgery, has been wearing a red non-contact jersey typically saved for quarterbacks and kickers.

The defensive line was hit even harder, with only seven players able to practice. End Lamarr Houston, one of just two holdover starters from Oakland's defense in 2012, has been out since Thursday. Tackles Pat Sims and Vance Walker were also missing from practice.

It's gotten so rough that defensive tackle Myles Wade, signed Wednesday because of the other injuries up front, was hurt in his first practice and has been out since.

Rookie linebacker Sio Moore, the team's fourth-round draft pick and likely starter on the strong side, did not practice either, nor did kick returner Josh Cribbs.

How serious the ailments are is unknown, at least outside of the Raiders training room. Allen has been hesitant to discuss injuries since camp began and did not change that approach Sunday.

None of them are major injuries,'' Allen said.Hopefully we'll get those guys back sooner than later.''

One player who might not be back anytime soon is second-round pick Menelik Watson. Watson has not practiced in training camp and has been limited to individual work in the weight room and riding a stationary bicycle.

He's way behind,'' Allen said.He went through the offseason program, but here we are in the second week of camp and he hasn't seen a down yet. He's got to get healthy and get back out here.''

With so many players missing, the Raiders decided to practice without pads to give the healthy players a break.

It's hard to get multiple groups of a defensive front when you've only got seven guys that are able to go,'' Allen said.We took the pads off and we slowed the tempo down at the end in the hopes that we can keep some of these guys that are having to take extra reps as fresh as we can.''

Notes: The Raiders signed two-time Pro Bowl long snapper Jon Condo to a three-year extension. That came on the heels of Oakland's decision to give kicker Sebastian Janikowski a four-year extension Friday. ... Ryan Baker, a backup defensive end for Miami the past four years, worked out for the Raiders after practice while Allen, general manager Reggie McKenzie and several scouts watched.