When Washington Redskins Coach Joe Gibbs met with his players this past week, he told them they could not afford to overlook the Detroit Lions, a team that seems quite easy to overlook since it never has won a football game in this city.

"They're coming off a big loss (their worst in five seasons, a 43-10 defeat by Green Bay), and we're coming off a great game (a 27-10 victory over St. Louis)," Gibbs said of today's 1 p.m. game at RFK Stadium.

"What does that sound like? Two weeks ago, we lose big to Chicago, and the Cardinals win big (over Green Bay). Then we beat them.

"I'm sure the same thing can happen here."

It's all a matter of how you look at it. The Lions (3-2), who beat Dallas the week after the Redskins lost to the Cowboys, don't look nearly as good statistically as they do in the standings.

They rank 26th in the NFL in offense and 27th in defense. They allowed the Packers 285 yards on the ground last Sunday, and because the Redskins (2-3) are ranked first in the league in rushing (186 yards per game), let's leave to the imagination the prospects for John Riggins and George Rogers today.

Then, consider what happened last week to the Lions: They fumbled six times, losing four, including one on a punt and another on a kickoff; they were intercepted twice; they gave up a safety and four sacks, and outside linebacker Jimmy Williams was ejected for fighting.

Sounds kind of like the Redskins of a few games ago.

Well, things are different now, say some at Redskin Park.

"I think we have to get our backs against the wall before we can play Redskin football," said defensive end Dexter Manley, who is tied with teammate Charles Mann for second place in the NFL with 6 1/2 sacks.

"It's not hard to get ready for anyone now. We can't afford to lose any more games, that's all."

After today, the Redskins will not play at home until Nov. 10 against the Cowboys. They play three consecutive games on the road: against the New York Giants, Cleveland and Atlanta.

Leaving with a 3-3 record certainly would be preferable to leaving at 2-4, especially with Dallas sitting pretty at 4-1 in the NFC East going into today.

Likewise, the Lions probably will find out how close they'll stick to the NFC Central-leading Chicago Bears after their next three games.

"We play Washington, San Francisco and Miami," said rookie Coach Darryl Rogers, pausing at the thought. "We'll have a better idea after those."

The Lions and Redskins have played five years in a row here. The last time Washington lost to Detroit was Oct. 3, 1965. Gibbs was a graduate assistant at San Diego State then; General Manager Bobby Beathard was a part-time scout with the Kansas City Chiefs.

But don't assume the Lions are pushovers. They have a new running back in place of injured Billy Sims: Wilbert Montgomery, who leads the team with 235 rushing yards in 69 carries (a 3.4-yard average).

In 13 games against the Redskins as a member of the Eagles, Montgomery averaged 4.4 yards per carry and scored 13 touchdowns, more than he has scored against any other team.

Fullback James Jones (a 4.7-yard average) is back after missing two games with a thigh injury.

Although Eric Hipple (67 completions in 133 attempts for 928 yards, six touchdowns and five interceptions) is the starter, Joe Ferguson, a former Buffalo quarterback, played for the first time last week (10 of 11, with one interception) and may play if things don't go well for the Lions this week.

And that is likely, considering that the Redskins' defense, consistent throughout the first part of the season, ranks third in the league and forced four interceptions of highly regarded Neil Lomax on Monday night.

The Lions also have a new 3-4 defense with Pro Bowl lineman Doug English now playing nose tackle. Their opportunistic defense worked rather well until it played the Packers; a plus-seven turnover ratio dwindled to a plus-two after that game.

The Redskins, of course, would rather not discuss turnover statistics. Their ratio is minus-eight.

"The Lions are a totally different team," said Gibbs, praising Rogers for going through his first five games with three more wins than Gibbs had in his first five in 1981.

"They had the real bad game last week, kind of what's been happening to us. I think that makes them more dangerous . . . The reason for that is, teams are very close these days in the NFL, and the team with the emotional edge winds up being the winner," Gibbs said.

"I think we're smart enough as a team to understand that."

The Redskins also understand that they win when they run (they are averaging five yards per carry this season), but they must do better when it comes to passing.

The Redskins' passing game is ranked last in the league, with only 142 yards per game. This is one of the reasons rookie Gary Clark will start in place of Calvin Muhammad.

Punter Steve Cox was examined by a neurologist, Dr. Bruce Ammerman, yesterday afternoon and was given a clean bill of health, Ammerman said. Until last week, team doctors were unaware that Cox, 27, had surgery in August 1983 to insert a shunt (tube) in his brain to allow spinal fluid to pass through.