The turnaround that has brought the Redskins three victories in their last four games has not assured Coach Joe Gibbs that his team is ready to compete successfully against some of the National Football League's better teams.

"We are good enough to play four good back-to-back games," Gibbs said yesterday. "But the teams we have beaten so far have had lesser records. We're going to begin a stretch now against teams that have winning records and are challenging for playoff berths. That will tell us something more."

That stretch will begin Sunday against Detroit in RFK Stadium. Although the Lions' record is 4-5, they are in contention for the NFC Central title.

After the Detroit game, the Redskins meet the New York Giants, Dallas, Buffalo and Philadelphia, all of whom have winning records. All but the Eagle game are on the road.

The Redskin victims were Chicago (2-7), New England (2-7) and St. Louis (3-6). But the decisive job on the Cardinals in Washington's 42-21 victory Sunday gave Gibbs reason to be optimistic about the rest of the season.

"We definitely are an improved team," he said. "The Cardinal game was our best by far. We played a solid all-around game, with all of our units playing well.

"But we are just getting our feet on the ground after that start we had. We are seeing who the producers are, people like John Riggins, Joe Washington and Mike Nelms. We are still juggling places, we are still trying to discover ourselves. But we are making real progress after being 0-5 and that is what I'm most happy about."

Gibbs listed five major reasons for the Redskins' recent improvement:

* Reduction of injuries. "A lot of guys are coming back, even though we still have people hurt," he said. "Getting the big-play guys back like Nelms is so important. You don't know until now how much you really missed them. If Mike had been healthy earlier, he might have given us a spark in some of those games that could have made a difference."

* Better understanding of personnel. "The longer we are together as coaches, the better we know our players. We have a better feel about who should be on the field in different situations. We know where to use John Riggins now, where a Joe Washington should be getting the ball. With so many new players, it took time to get things down."

* Switch to a one-back, two-tight-end offense. "Ever since then, we've done a lot better offensively. It's something I debated using when I first came here, but I decided to use two backs. And the success we had in preseason with two backs might have been misleading."

* Fewer mistakes. "We were our own worst enemy earlier in the season," he said. "Now we are playing much more consistently. We've cut down on our turnovers and our penalties and our takeaways have increased. We are doing a better job protecting the ball. We've only got two running backs handling it (Riggins and Washington) and that helps, and Joe (Theismann) is more in a groove. He's not throwing as many interceptions."

* Improved confidence. "The first part of the year, you say, 'Goodness gracious, when are we going to win?' You have nothing but repeated failure. Now we think we can make the right plays, we think we are a good team."

From a team that seemed determined to undermine its ability to win every week, the Redskins have become more efficient and more competitive even though they are not yet completely healthy.

Washington can't match up in personnel with many of the better teams, but by reducing mistakes it has been forcing opponents to work harder instead of helping them with timely turnovers.

During their 0-5 start, the Redskins threw 11 interceptions, lost 10 fumbles and were penalized 41 times for 401 yards. In the last four games, since going with a one-back offense and letting Riggins and Washington carry the ball almost exclusively, they have had two interceptions, lost four fumbles and been penalized 13 times for 209 yards.

In this span, Riggins has rushed for 296 yards (he had 122 the first five games) and Washington has gained 294 yards (49 in the first five).

Although the Redskin defense has begun to yield more passing yards, it has increased its total of takeaways. After five games, it had three interceptions and three fumble recoveries. Over the last four games, the defense intercepted 10 passes and recovered three more fumbles.

Theismann had thrown nine interceptions the first five weeks, but has had two interceptions the last four Sundays and has gone two games and 59 straight attempts without an interception. He completed 69 percent of his passes (45 of 65) the last three weeks.

The Redskins signed Cris Crissy, a defensive back/wide receiver, for the third time this season and released guard Robert Woods . . . Nelms moved to first in the NFC in kickoff returns and third in punts after his game against the Cardinals. Since coming back from a broken thumb, he has had four kickoff returns and three punt returns of more than 40 yards. "We gave him a Superman shirt for the way he played Sunday," Gibbs said . . . Riggins needs 34 yards to become the NFL's eighth all-time rusher . . . Tight end Don Warren has caught passes in 20 consecutive games . . . Middle linebacker Neal Olkewicz and free safety Mark Murphy both have more than 100 tackles this season to rank 1-2 on the team . . . Tackle Joe Jacoby, in his first start for Mark May, and linebacker Mel Kaufman, replacing the injured Brad Dusek, had fine games. "It was hard to find someone who didn't play well," Gibbs said.