OAKLAND, Calif. — Oakland's fourth-round draft pick Bruce Campbell went through an emotional grind as he sat through nearly two days of the NFL draft before hearing his name.

Having to make a position change seems easy by comparison for the Raiders rookie.

Campbell, projected as a first-round pick at left tackle in many mock drafts, has been working out exclusively at right guard with the second-team offense during Oakland's three-day mandatory minicamp.

Coach Tom Cable said the decision to move Campbell was made to get the former Maryland star work rather than burying him on the depth chart at tackle.

The Raiders have had success doing this in the past. Robert Gallery, the No. 2 overall draft pick in 2004, was moved to left guard after struggling at both tackle positions and has developed into Oakland's most accomplished offensive lineman.

"This is actually my first time playing offensive guard and my first time on the right side," Campbell said. "It's just football. It's still the same thing, just that I have a little more help and I'm inside. It's not that bad at all."

Campbell has had bigger challenges to overcome in his past.

As a sophomore he underwent brain surgery to relieve pressure, a condition brought on by his body growing too fast for his bones.

After a slow start to his career at Maryland, the 6-foot-6, 315-pound Campbell emerged as the Terps' strongest and most consistent lineman and worked his way up the draft boards with a solid but unspectacular junior season.

Oakland informed Campbell he'd be moving from the left side of the offensive line to the right shortly after making him the 106th overall pick in the draft.

What they didn't say was that Campbell, who wowed scouts at the NFL Combine when he was clocked under 4.8 seconds in the 40-yard dash, would be switching from tackle to guard.

"That's where I want to start him," Cable said. "This gives him a chance to get in that second huddle where he's going to get a lot of work and we can start his development right away, rather than retard it if he's getting a few reps as a third (tackle)."

Campbell had his rough moments Sunday, false starting twice during team drills while working with Oakland's second-team offense.

His primary focus, though, has been on proving critics wrong. The knock on Campbell is that he is more flash than substance, an idea that picked up steam following his workout at the combine where he also bench-pressed 225 pounds 34 times.

That likely factored into Campbell's freefall on draft day.

"I got a little worried as I was watching the draft and didn't see my name picked," Campbell said. "I was like, 'Hey, what's my next step? Am I going to have to walk on to a team?' But after my name got picked, it was a sigh of relief and I calmed down.

"I wasn't surprised because I kind of knew it was going to happen after my combine. I knew all the negative talk was going to come into play so I was kind of prepared for it. I have a little chip on my shoulder that I really can play football and I'm not just an athlete."

NOTES: Safeties Michael Huff and Tyvon Branch spent part of Sunday's practice playing cornerback to get more comfortable playing in man coverage. ... WR Louis Murphy (ankle) sat out, as did fellow receiver Chaz Schilens (foot) and CB Chris Johnson (back).