Tom Landry calls it a predominantly passing offense, yet John Riggins is supplying 42 percent of the Redskins' playoff yardage. And Riggins hasn't thrown a pass in his 11-year career.

The Redskins' offense looks simple when Riggins is running, yet it is among the league's most complicated.

It relies heavily on the abilities of its quarterback to read defenses and make on-the-move decisions. No other offense in the NFL may depend quite so much on one player's instincts.

"I think people judge us on preconceived notions," said Coach Joe Gibbs, whose work as San Diego's offensive coordinator led to his job in Washington. "Because we passed so much in San Diego, people think that is the only thing this offense can do, even if John is running a lot now. I like to think we can tailor it to the skills of the people we have.

"What I want is balance. You try to mix both run and pass and then you go with what is working best in each game. But you go in trying to do both about equally."

Gibbs' offense hasn't produced the statistics projected when he was hired, but it has produced victories. Since switching to his one-back, two-tight-end formation (an offense he designed in San Diego), the Redskins are 19-4.

"What's so impressive about the offense is that everything we do is very sound," quarterback Joe Theismann said. "Joe doesn't ask us to do anything that is a gamble, that won't work if we execute it right."

When Riggins is bulldozing up the middle, the offense may look like a version of Woody Hayes' much-criticized cloud of dust. It isn't.

"So much of what we do stems from things like motion and formations," Theismann said. "By moving people around, we can create mismatches on defense and take away support from areas that will allow us to run better to those spots. Just using two tight ends to block instead of relying on a smaller running back as a lead blocker also makes sense,and helps you to run better."

Motion is blended with power-blocking techniques practiced by the offensive linemen. This is a new approach to run blocking; Redskin linemen are taught to be overly aggressive, to go after defensive linemen and use their arms to push off, instead of accepting blows with their elbows. That's one reason the Redskins like big, strong linemen instead of sleeker, quicker athletes.

"What you have is the classic attempt to blend running and passing," Theismann said.

When the Redskins pass, Theismann is responsible for going where the defense isn't. Gibbs claims his team never calls a pass directed at a specific individual. Instead, the Redskins usually send three or four receivers into every pattern; Theismann may look mostly to one side of the field, but he will select from a number of possible receivers before throwing. In theory, if the patterns and timing are coordinated, a defense can't stop this approach.

And within every passing call is a built-in long pass. "We don't have to force a big play," Theismann said. "It's there if I want to take it. That's what it comes down to: my judgments built on the study I've put in that week and Joe's game plan.

"If you are patient, the plays are there and the yardage is there. Defenses just can't cover everything."

The offense will change as personnel changes. The more versatile his players, the more experienced they become, the more innovation Gibbs will employ. But for now, he has one aim: attempt high-percentage plays that will eliminate turnovers, allow ball control and make sure that if the Redskins don't score, opponents will get poor field position.

These theories work. The Redskins have committed just one turnover in the playoffs, Riggins has gained 444 yards, they have averaged 27 points a game and playoff opponents have begun just one of 30 series in Washington territory. "It's working like it's supposed to," Theismann said. "I just hope we can wind it up right for one more game."