Raiders CB Shawntae Spencer bit on a move and watched as WR Darrius Heyward-Bey raced by him down the left sideline at practice Saturday afternoon.

It was that kind of day for Spencer, a former 49er who has struggled with his new team.

“I think he’s been a little up and down in camp,” Raiders coach Dennis Allen said. “We’re going to continue to push him and see where he’s at. I’m not pushing the panic button on him yet. Obviously with all these guys we want to continue to see improvement.”

The Raiders signed Spencer as a free agent, and he’s been working with the first team at right corner. He has 72 career starts, but last year he didn’t start a game for the 49ers and appeared in only nine. The 49ers released him after the season.

That’s a definite red flag for a CB who turned 30 in February and is entering his ninth season.

Ivey still working his way back: Travis Ivey, the only true NT on the roster, reported to training camp out of shape and hasn’t been allowed to practice with his teammates.

“It’s a safety issue as much as it is anything else,” Allen said. “I want to make sure that he’s healthy, in shape, conditioned, his weight is where it needs to be so that if and when he does get out here and start practicing that he doesn’t injure himself.”

Ivey, who was signed to the Raiders’ practice squad in December, is listed at 341 pounds. He’s the heaviest Raider.

Ivey spent 15 weeks on the Cleveland Browns practice squad in 2010 and was on the 53-man roster for the final two games, making one appearance. The Browns waived him Sept. 3.

Moore battling hamstring injury: WR Denarius Moore said when he reported to camp he felt “100 percent” healthy and completely recovered from a hamstring injury he suffered in minicamp. But he tweaked the injury Tuesday and missed Wednesday’s practice. Then on Saturday he quit practice early because of the injury.

Moore said he’s “just being careful right now” and trying to avoid making the injury worse.

“It’s when the pain comes, when it comes and bites me, that’s really what it is,” Moore said. “It’s just seeing what I can do each day, and then is the strength getting better or worse?”

As a rookie last year, Moore caught 33 passes for 618 yards and five touchdowns, averaging 18.7 yards per catch. Moore has been working with the first team, when healthy, paired with wide receiver Darrius Heyward-Bey.

“I got a chance to see him last year up close and personal, so I know what type of player that he is and what he’s capable of being,” said Allen, Denver’s defensive coordinator last season. “Those hamstrings can be a nagging deal, so we’re going to be cautious to make sure that at the end of the day we’ve got him ready to go come the Monday night opener (against San Diego). That’s really what we’re shooting for. We’re going to try not to put him in a position where he sets himself back a lot.”

Moore said he has no choice but to be patient.

“It’s a little frustrating coming in, knowing that you have an injury, have to sit out and wait and watch your teammates constantly practice, going through it and grinding, and you just sit on the side,” Moore said. “But it’s something that you can’t control, you’ve got to sit back and just let it heal on its own.”

Follow Raiders reporter Eric Gilmore on Twitter: @CBSSportsNFLOAK.