While Joe Theismann is studying flex defenses and talking up a storm and Diron Talbert is hankering to scalp Dallas for the umpteenth time in his seemingly endless career, Terry Hermeling is just plain glum.

And that, his Redskin coaches say, ranks with anything Theismann and Talbert do as an indication Washington is preparing properly for its showdown Sunday with the Cowboys.

When Hermeling has that certain cantankerous look on his face, when he acts as if he had eaten rotten eggs for lunch, the coaches love it.

"He gets that way before any game against a great opponent," said Ray Callahan, offensive line coach who is fighting a case of the jitters himself. "Terry is the kind of guy who can play above his true ability when he has to face a Harvey Martin. He's a marvel at preparing himself for these tests."

Down in the trenches, where Hermeling and his offensive linemates romp on NFL Sunday afternoons, there is a lot of self-motivation talking place.

For all the talk about injuries and hot passers and verbal warfare, they know where this game will be decided. And they don't want to ruin what has been a splendid season for them with one atrocious performance.

That's why Coach Jack Pardee hovers over guard Jeff Williams every day, checking carefully on the progress of Williams' injured knee. That's why the staff hopes Hermeling is growling at everyone by the end of the weekend and that guard Ron Saul's ankle is completely healed and that center Bob Kuziel keeps improving, as he has almost weekly.

And that's why this line is so high these days. This is Dallas week. This is what tackle George Starke calls "a fun time." This is when all the work in the hot, muggy days of Carlisle training camp could pay off.

This may not be the best offensive line in the league, but it is vastly improved over the unit that took the field against Dallas this time last year.

For the most part, the line has stayed healthy, avoiding the kind of crippling injury that sidelined Starke last season and started a slide to disaster.

The horrible sack total of 1978 (48) has been reduced to 30 -- and only 11 1/2 of those are attributed completely to a breakdown by the line.

The running game has picked up late in the season, John Riggins again is a 1,000-yard rusher and the things the line had problems doing last year -- grinding out short-yardage first downs, for example -- have been reduced considerably.

"We are stronger and more physical," Starke said. "We'll get better, too. A unit has to play together probably a couple of years to reach maximum efficiency. That's why there is room for progress."

Starke (seven years), Hermeling (10 years) and Saul (10 years) represent the experienced portion of the line. Kuziel (five years) became a starter last year; Williams (Two years) was added this season and promises to develop into the best of the bunch, a potential all-pro.

Except for a breakdown against New Orleans (six sacks, poor goal-line offense), these five have held up well during the season in which they were clearly on the spot. Pardee and Callahan told them they had to get better and they responded, especially with fine pass protection.

"I don't think Joe could have had the kind of year he has if we hadn't blocked well," Kuziel said. "He's helped with a quick release and a lot of short passes. But we feel good about that and we feel good about John gaining 1,000 yards. It would be embarrassing not having him gain 1,000 yards."

Riggins, however, says that the line "hasn't got all the credit it deserves.They've been overlooked. Their improvement has got as much to do with why we are 10-5 than anything else. They've maintained a high level of consistency all season."

But all that is history. Dallas is the present: the Doomsday defense, the flex formations, the kind of attitude Kuziel say "makes you want to play well so badly it can hurt."

Hermeling and Martin have engaged in ferocious matchups in the past. Starke has encountered end John Dutton only once, but even this former Pro Bowler is welcomed when the alternative could be Too Tall Jones. Ron Saul is much more familiar with tackle Larry Cole. And Williams knows enough about Randy White to work extra hard on getting that knee healthy.

"He is so quick," Williams says of White, who played only briefly when Dallas lost in RFK Stadium a month ago. "It's going to be an awfully interesting afternoon."

Williams represents the prototype lineman Pardee wants to work into this line. He is big (265 pounds), strong, physical and competitive. He also is finishing off his first year at a position which still gives him fits.

"Thank God for Bob," Williams said, pointing toward Kuziel. "He's pulled me through this season. He's had to know his assignments and mine, just to make sure I knew what I was doing."

But just think, said Callahan, "what Jeff will be like with more experience. Whew, what a player. He has what you want: quick feet, strength, good speed and a fine attitude. He can be as good as anyone."

White, however, already is as good as any NFL defensive tackle, as long as his bad ankle holds up. This may be a game when Williams receives plenty of double-team help from Kuziel as well as verbal instructions.

The Saul-Cole matchup is one for purists. Both are no-names with 22 years of league experience between them. But each represents the image of true trenchman: gutty, dedicated, uncomplaining and professional.

Saul, shaped like a fire plug, is shaking off a slump caused by those ankle problems. This is his kind of game and Callahan is certain Saul will be ready.

"You'll never hear a complaint from Ronny," Callahan said. "Sometimes that hurts because ailments can bother his play. But you know on game day, he'll be in uniform and you have to order him off the field before he'd leave.

Starke is the thinking man's tackle. He brings an eloquence to the game that makes complicated issues seem simple. He also is enjoying his finest season, grading out the highest of any lineman, and putting to rest any fears about his bad knee.

"My knee really hasn't been a consideration since last January, when it felt okay," he said. "But I came to camp in the best shape in my life, just to be sure the knee and everything else was ready.

"I should be playing well. I'm in the prime of my career, I'm at the age where everything I've learned should come to use."

He seems out of place in the line, this lover of films and the finer things in life. But Starke derives pleasure out of duels with opponents like Dutton, realizing full well it takes a combination of both brains and brawn to prevail.

His approach contrasts sharply with that of Hermeling, who has overcome knee problems with extra weight work to remain a front-line player. Hermeling can be irascible and loud, but he is enough of a leader to be selected, along with Starke, as a team captain.

"There is a good reason why we love this week so much," said Kuziel, whom Callahan thinks is the smartest center in the league.

"Dallas never does anything different. All of us know when they will dog, when they are going to pass. They just say, 'Okay, try and stop us if you can.'

"That's a challenge, pure and simple. It's what we've been working for since training camp.If we are good enough, we can handle whatever they throw at us."