DT Justin Harrell (right) battles through a block in Saturday's opening practice.

The starting battle between defensive tackles Corey Williams and rookie first-round draft pick Justin Harrell promises to be a spirited one, but both players are approaching it with the right attitude.

Williams, a fourth-year pro coming off a seven-sack season in 2006, said he's simply going to play hard, do his job every day, and let the depth chart take care of itself. Williams was in the lineup with the No. 1 defense for Saturday's opening practice, but he said he's not going to let the competition get in the way of being a good teammate.

"I'm going to try to help my teammates," Williams said. "Justin, he's a great guy, he's a hard player. If there's something I can help him with, I'm going to help him."

Meanwhile Harrell, who was in pads Saturday for the first time since last September due to the ruptured bicep sustained his senior season in college, is just focusing on getting back into football shape after the long layoff.

Harrell participated in individual drills but was held out of all team (11-on-11) periods during mini-camps and OTAs. He was back in for team drills on Saturday, working with the second defense.

"You can go out there and run sprints and things like that, but it's a different kind of conditioning going out there and playing football," Harrell said. "It's been a long time since I've been in pads and hitting somebody, and I'm real rusty."

Harrell doesn't think it will take too long for him to knock the rust off, and he has every intention of competing for a starting spot. Williams, who admitted he's even more motivated by the fact that he's in the final year of his contract, wouldn't have it any other way.

"I love competition," Williams said. "I don't want them to give me anything. I want to go out and work hard.

"I'm just going to go out there and do my thing and let them decide on who's going to be No. 1."

Injury, participation update

Wide receiver Donald Driver did not practice after failing his physical on Friday, but he believes he'll be back on the field within a few days. Driver is still feeling some effects from the right shoulder injury he sustained last December in the game at San Francisco. He played through the injury the rest of last season, but the team doctors did not believe he should participate in a full-pads practice yet.

"Right now when I stretch my arms out, doc pushes it down with ease, so it's not strong enough for me to take a pounding," Driver said. "He wanted to make sure I was able to do that before I step on the field."

McCarthy said Driver's availability would be day-to-day.

"I'm not concerned because I think like all of us know that Donald keeps himself in excellent shape all year round," McCarthy said. "This is something that bothered him coming into camp, so we're just being cautious him."

Three other players did not practice - defensive tackles Ryan Pickett and Johnny Jolly, and rookie running back DeShawn Wynn. McCarthy said Pickett and Jolly did not pass the running test that's part of every player's pre-camp physical on Friday, so their conditioning is not good enough for them to practice and they are day-to-day. Pickett was replaced on the No. 1 defense by Colin Cole.

Wynn is suffering from a stomach virus, and it's unknown how long he'll be out.

Tight end Tory Humphrey injured an ankle during practice and was carted off the field. The severity of the injury wasn't known, but it appears he could miss some significant time.

Back at it, finally

The few snaps he slipped into the defensive backfield during the final week of OTAs notwithstanding, safety Marviel Underwood was back at practice for full-time duty for the first time since injuring his knee in the preseason opener last season.

In short, it was a long wait for the third-year defensive back, who did his weightlifting workout a little after 7 a.m. Saturday and had several hours to think about returning to practice.

"It was a long day," he said. "I was just waiting. I couldn't wait to go out there, put on my pads and my cleats and go out there and perform."

Underwood was having a terrific training camp last summer when he went down, and he hopes to pick up where he left off and challenge for the starting safety spot alongside Nick Collins this year. For the first practice, he was taking snaps with the second and third defensive units, with Marquand Manuel and Collins on the first unit.

"I'm just trying to stay healthy and make plays and let the coaches sort it out," Underwood said. "If they put me out there, I'm going to be ready."

{sportsad300}Strong early impression

Backup cornerback Tramon Williams, who has a long battle ahead for a roster spot amidst the team's large number of defensive backs, was all around the ball all day and appeared to make a good first impression in camp.

Twice Williams was one-on-one down the sideline on a jump ball with Carlyle Holiday and was able to break up the play. He played similarly tight coverage on a deep pass to Calvin Russell as well.

Bouncing back

Veteran receiver Robert Ferguson had one early drop on a fly pattern during a one-on-one drill against cornerback Charles Woodson, but he came back in the next team period with a big play, catching a long pass in stride from Brett Favre.

In another team period, he also made a strong catch against tight coverage by Jarrett Bush on a comeback route.

Similarly, third-string quarterback Ingle Martin followed up a poor throw with a dynamite one during seven-on-seven drills. One play after getting nearly picked off by Will Blackmon, Martin threaded the needle between defenders Desmond Bishop and Frank Walker to Chris Francies, who came up with the tough catch.

New holder

It appears for the kicking competition between Dave Rayner and Mason Crosby that punter Jon Ryan will hold for Rayner, as he did all of last season, and receiver Ruvell Martin will be Crosby's holder.

Martin is the backup holder on the depth chart, and it will be important for him to take a lot of snaps as a holder in case Ryan gets injured or is beat out by Australian David Lonie for the punting job.

Martin said after practice he will likely hold for both kickers as training camp continues.