By R.B. Fallstrom ~ The Associated Press

ST. LOUIS -- When Aeneas Williams began rehabilitating from a broken leg and torn ankle ligaments that cost him the second half of last season, a move from cornerback to safety was out of the question.

In the opener on Sunday, though, that's where he'll be for the St. Louis Rams. A combination of need and a concession to age pushed Williams, 35, a seven-time Pro Bowler, to a new position where the Rams believe he'll thrive.

After losing Jason Sehorn and Kim Herring to injuries in training camp, coach Mike Martz joked that it took "about a day" to persuade Williams to try free safety. That's only exaggerating a bit. Martz knew Williams would work out during his first practice when Kurt Warner tried to look him off the ball and Williams quickly recovered to make an interception in the end zone.

"When he got back there he was having so much fun he was shocked at what he could see," Martz said. "He has a certain gift that is very unusual that we need to be able to take advantage of."

The move may not be permanent, depending on the Rams' needs later in the year. Herring was released but Sehorn is expected back from a broken foot in mid-October.

"We'll just see how things go when Jason gets back," Martz said. "Aeneas may end up back at corner."

The only problem in Williams' conversion has been getting on the field, a decision by Martz to preserve him for the season. He appeared in only one preseason game and rarely has practiced to allow the break and the ligaments to heal, as well as to allow a year-old turf toe to quiet down.

"In the preseason we played a lot of games on turf and we just didn't see the benefit of putting a lot of pounding on his entire body before the season," defensive coordinator Lovie Smith said.

No one on the Rams practices harder than Williams, who sets an example for the team's younger players with his work ethic. But he didn't seem to mind watching as the Rams saved him for the games that count.

"I was able to shift into another aspect of the game, and that's taking mental reps," Williams said. "Sometimes it's maybe more important than the actual physical stuff for me.

"Physically I know I'll be fine, so making the mental transition to safety was extremely important."

Williams is 100 percent heading into Sunday's opener at New York against the Giants.

"He's ready to go," defensive coordinator Lovie Smith said. "We want all of our best players on the field, and that's what we've got."

Williams has no arguments over the treatment.

"The time off helped," Williams said. "The wisdom of the coaches is always better because I probably would have practiced every practice and done everything that I normally do."

The Rams are looking to Williams as a calming veteran hand in a secondary that has a total of five years' experience. The cornerbacks are second-year man Travis Fisher and Jerametrius Butler, a fifth-round pick in 2001 who played sparingly last year, and the strong safety is Adam Archuleta, a first-rounder in 2001.

"It's going to work out well," Williams said. "The good thing is the young guys got a lot of opportunities to make plays and get experience in the preseason as much as possible.

"I think they'll be ready to play."

Just as important for the Rams, Williams will be ready, too.