SAN DIEGO -- When speaking of All-Pro nose tackle Jamal Williams' value to the Chargers' defense, the proof is in the ranking and what his teammates say about him.

The Chargers' rushing defense has ranked among the NFL's top 10 in seven of Williams' nine seasons, including seventh last year. So Williams' importance as the anchor of the team's 3-4 scheme cannot be overstated.

"That's the one that we can't replace," outside linebacker Shaun Phillips said. "He's the best in the business."

Added defensive end Luis Castillo: "I'll say this. As many talented players as we have on this team offensively and defensively -- especially defensively when you look at guys like Shawne Merriman and Shaun Phillips, the pass rushers we have, the defensive ends, and some of the great cornerbacks -- none of it works without that man in the middle."

The Chargers avoided a serious blow to their defense this week when an MRI exam revealed that the foot injury Williams suffered during Sunday's exhibition loss to the Seattle Seahawks was nothing more than a sprain.

Williams, who has started in back-to-back Pro Bowls, is listed as day-to-day.

"We're fortunate that it's just (a sprain)," said Williams, who was wearing a protective boot on his left leg Tuesday. "We were worried about it at first. (The trainers) saw how the swelling was. But after that, everything has looked good. The swelling is going down. Hopefully I'll get some time this weekend."

But should Williams risk further injury on a fragile foot during preseason games?

"I expect him to be back and be ready to play in the preseason games," said Chargers coach Norv Turner, though Williams' status for Saturday's game against the St. Louis Rams is in question.

Second-year defensive tackle Brandon McKinney, a former undrafted rookie free agent, took reps with the first team in place of Williams.

Legedu can do

It was expected that rookie wide receiver Craig Davis, a first-round pick from LSU, would make an immediate contribution.

But Legedu Naanee?

Drafted in the fifth round out of Boise State, Naanee played more than he expected to against the Seahawks. He had four catches for 44 yards and impressed Turner in his first NFL game.

"He certainly has had a good training camp and he made, I think, a very positive impression in his first competition," Turner said. "He truly has something that I think he can feel good about and something he can build on."

With Eric Parker out for about eight weeks and question marks surrounding the receiving corps., Naanee finds himself in the mix and figures to be among the Chargers' primary targets this season.

"The coaches kind of stressed a point that they want to see somebody come out in these preseason games and make a statement that they can contribute and that they're ready to play," Naanee said. "That's where my focus is -- showing them that I can contribute early."

Ready for a half

Turner's announcement that he plans to let the starters play the first half of Saturday's game at St. Louis was music to quarterback Phillip Rivers' ears.

"I think that's good to be able to go in and put a string of drives together," Rivers said. "Sometimes when you only get two series, it's hard to gauge anything. With a half, we should really be able to get into a rhythm and see if we can get in sync like we want to."

Injury update

Safety Eric Weddle (ankle) was the only player injured during Sunday's game who practiced on Tuesday. Linebackers Anthony Waters (knee), Marques Harris (shoulder) and Jyles Tucker (concussion), and cornerback Steve Gregory (quadriceps contusion) didn't practice, but Turner said he felt optimistic about their returns.

"From a standpoint of where we were yesterday, I think it's a positive prognosis of when we'll get them back," Turner said.

Contact staff writer Simon Samano at simon_samano@yahoo.com. Comment at nctimes.com.