It was no secret the Washington Redskins were capable of scoring 31 points in a game. It also was no secret they were capable of allowing 31.

But in their season opener against the Phoenix Cardinals yesterday at RFK Stadium, the Redskins scored 31 and didn't allow any. For a team whose defense was plastered with more question marks than a book of knock-knock jokes, Washington had an awful lot of answers.

"I don't know if we can turn it up any higher than we did today," defensive end Charles Mann said. "We played hard."

The Redskins came away with five turnovers, three sacks and their first shutout in a season opener since 1973, when they victimized the San Diego Chargers. In case you need a frame of reference, Johnny Unitas played quarterback for the Chargers that day.

But to frame yesterday's game, keep in mind the Cardinals were playing their first game under Coach Joe Bugel and their quarterback, Timm Rosenbach, was making his second NFL start. Also, this was just the first of 16 games -- and the two-time defending world champion 49ers await next Sunday at Candlestick Park.

Asked about a Redskins pass rush that sacked Rosenbach three times and raised considerably more havoc than that, Mann said: "It's still a question."

Asked about a Redskins secondary that intercepted four passes, strong safety Alvin Walton said: "We know we still have a lot of improving to do. This wasn't the best. As a team, we made a lot of mistakes on defense. When we go against a better team like San Francisco, we can't make too many mistakes."

However, the Redskins defense played spirited, opportunistic, aggressive football. They did what they were supposed to do against a young quarterback. They presented him with a kaleidoscopic system and kept it, and him, spinning.

"We tried to keep people in his face," Mann said. "We didn't want him to get anything going. We wanted to keep him down."

They did a good job of keeping him down and keeping him guessing.

"They would line up in one look and then move into another look," Rosenbach said.

And there were other changes afoot. For example, instead of having Darrell Green stage his usual duel against Roy Green, they played a lot of zone pass coverage.

"It was weird," Darrell Green said. "I'm used to chasing the guy all over the field."

But it's tough to argue with the results. Roy Green and J.T. Smith, who have made the Redskins miserable on many occasions, hardly factored into the equation yesterday. Washington cornerback Martin Mayhew made as many interceptions as Roy Green made receptions (two). Darrell Green and Walton each matched Smith's one-reception output, with Walton returning his prize 57 yards for a touchdown.

"Defenses nowadays have to make things happen," Mann said. "We made things happen with the turnovers."

It was a particularly rewarding afternoon for Mayhew, who said he had not intercepted a pass in a regular season game since 1985, when he was a sophomore at Florida State.

"I had almost forgotten what the feeling was like," he said in front of a locker that contained a game ball.

But he is well-acquainted with the feeling of being a marked man in the Redskins secondary. He knows that if opposing teams have to choose between picking on Darrell Green and picking on Martin Mayhew, they are going to pick on Martin Mayhew.

"Definitely," he said. "I mean, they would have to be stupid not to. I think I'm going to get a lot of throws. But it doesn't bother me. I think it's going to be beneficial. I think it's going to make me make more plays."

And Green thinks Mayhew is capable of making the plays.

"He has played great this preseason, and he played well here," said Green. "I think it's not fair to say every week, 'Well what about Mayhew?' You hope that he can finally get to a place you'll take it for granted that he's going to play well. . . . I think today is going to be a tremendous boost for him if he's been having the type of attitude in his mind that he's second to somebody else. But I don't think he has."

Said Mayhew: "I'm not trying to prove myself to anybody, I'm trying to improve myself. I think I can play. I know I can play. I just go out and try to play better every week."

The same is true among Washington's defensive linemen, who know they will keep being tested.

"We have 15 more games," defensive tackle Tracy Rocker said. "If we don't get a good pass rush next week, you know it will be back to, 'The Redskins don't have any pass rush.' We know we have a good defense. It's up to us. We have to keep it up."