Eric Williams joined the Washington Redskins yesterday morning, announcing he is a happy camper and that he welcomes the opportunity to play for a contender.

Williams criticized his former team, the Detroit Lions, for "having no class" and "lying to me about the trade," but said he'd asked to be traded to Washington several times during the past several months.

He said he "was born to play tackle in a 4-3 defense," and the Redskins will give him that chance beginning Sunday at Candlestick Park against the San Francisco 49ers.

His arrival came on a day when the team got another piece of good news from an ever-changing defensive line. The Redskins traded running back James Wilder and a fourth-round draft choice to Detroit for Williams on Tuesday because they were uncertain how much end Fred Stokes would be able to play the rest of this season.

But yesterday Stokes took part in a full practice and almost certainly will play against the 49ers. Not only that, the Redskins are more convinced than ever that Stokes may have a productive season.

His left shoulder popped out of place three times during Sunday's 31-0 victory over Phoenix. But the soreness in the area has decreased each day since the injury, and as trainer Bubba Tyer said: "As it's turning out, he's not even missing a day of practice. That's not too bad."

Tyer also has ordered a new harness for Stokes, and over the course of considering different treatments, Redskins linebackers coach Larry Peccatiello told him about his son, who played an entire high school season with the shoulder popping out "five or six times a game."

Likewise, Stokes is hopeful.

"It felt pretty good out there," he said. "I wasn't going to do anything to hurt it, but I did everything. The difference was that sometimes you're more active running around and all, and today I didn't do much of that. Right now, I feel I can play as much as they want and do whatever they want."

If he's right, the Redskins would have their deepest defensive line in years. Only six weeks ago, line coach Torgy Torgeson was offering as starters Charles Mann and three players who didn't make the team.

Now, he has his starting group of Mann, Tracy Rocker, Darryl Grant and Markus Koch (who probably got the highest grade of any defender). Stokes and newcomer Tim Johnson will come off the bench in pass-rush situations, and Williams will be used as a tackle on both running and passing downs.

In about six weeks, the Redskins have turned a weakness into a strength. Scouts say Williams is excellent against the rush and a decent pass-rusher, and the team especially likes the fact he has started for five years and, thus, been through a few battles.

"I'll use all seven of them," Torgeson said. "I like to keep fresh guys in there, and with the way people are substituted, it really shouldn't matter who starts and who doesn't."

Much will depend on what kind of shape Williams is in. Having not played a game this season, he said, "I've run and lifted weights, but to be in shape for football you have to play. It'll take time."

A reserve role would be a new experience for Williams, 28, who has started the last five seasons at end and nose tackle for the Lions. He had started 43 straight games when he was left off the active roster before Sunday's loss to Tampa Bay.

But that game came only three days after he'd ended a two-month holdout in a contract dispute that seemingly grew more bitter by the day.

Williams said yesterday he signed the contract only because the Lions promised he wouldn't be traded. He said that's why he showed up at camp and signed a one-year, $425,000 contract. Six days later, he'd been traded.

"It wasn't handled the way a class organization would handle something," he said. "I don't argue with the trade because that's part of this business, and it's the profession I've chosen. But I'm a man of my word and when someone lies to me, I don't like it."

Williams said that when he signed the contract, Lions General Manager Chuck Schmidt shook his hand and repeated the promise: "You're not going to be traded."

Schmidt denied that yesterday, asking: "Why would he be upset about being traded to a place where he'd asked to go? No, I didn't make him any promises. If I were going to promise anyone that, the guy I'd promise would be Barry Sanders, not Eric Williams."

Williams left more than teammates behind in Detroit. He's articulate and personable and had a radio show and a television show, "Gridiron Gourmet," in which "the idea was to show people that any slob -- I was the slob -- could cook something good."

He also left friends behind, but he was greeted by a couple of familiar faces at Redskin Park, where the starting quarterback, Mark Rypien, was a college teammate at Washington State, and one of the receivers, Walter Stanley, is a former Lion.

"I've wanted to come here a long time and I'll be happy about it," he said. "I was definitely in a comfort zone in Detroit and sometimes you have to break out of your comfort zone before you can improve. That'll happen here."

Williams said his troubles with the Lions began after last season when he said Schmidt told him he wasn't worth the money he was making ($385,000). Williams said he wanted to be traded and had heard the Redskins might be interested.

"I was so certain I was gone that I cleaned out my locker," he said. "We talked again at minicamp and they said I wasn't worth any raise whatsoever. What's there to talk about? I came in, got a small raise and a promise I wouldn't be traded."

As he spoke, Rypien walked past and, mimicking a reporter, asked: "Hey, can you still play in this league?"

Williams smiled and said: "We were in fraternities across the street from each other, and we'd pelt his house with snowballs in the winter and water balloons in the summer. I don't know what he's like with a football, but he couldn't hit the side of a house with a snowball."

Williams wasn't allowed to practice with the Redskins yesterday because, technically, the trade won't be finalized until Wilder has passed a physical in Detroit.

Wilder, who was unavailable for comment, was scheduled to arrive in Detroit late last night and take the physical yesterday morning, which would clear Williams to practice this afternoon.

On the other side of the trade, the timing could have been worse. Wilder, a Plan B signee last spring, picked his wife up at Dulles Airport on Monday and drove her and his family to their newly rented home in Northern Virginia.

Late Tuesday, General Manager Charley Casserly drove to Wilder's home to tell him of the trade and, moments later, Joe Gibbs phoned.