As Brad Dusek was walking toward the nursery of his Herndon home, he couldn't figure out where that "thump-thump-thump" was coming from. He got his answer when he opened the door and found 1-year-old William Bradley (Bucky) Dusek, bopping his head against the wall. And laughing.

"Yeah, the little guy was really going at it," Dusek said.

You will pardon him for smiling just a bit. Of such hard-headed stuff are NFL linebackers made, and no one knows that better than Bucky's father.

Six days ago, Brad Dusek was doing some serious head-knocking of his own against the Atlanta Falcons. For his efforts in the Redskin victory that day, he earned a game ball. He made a half-dozen solo tackles and two assists, sacked the quarterback once and deflected a pass.

Dusek's most important reward probably came two days later when he started and finished practice at his usual left lineback position, the spot he should occupy all day against the Cardinals Sunday.

There had been speculation that Dusek might be asked to go back to the special teams after Chris Hanburger returned to the starting lineup. Surely, George Allen would have to find a spot in the lineup for veteran Mike Curtis, Hanburger's replacement the last three weeks.

It now appears Curtis will be the odd man out.

He probably will fill in for hanburger, who is still down in weight and weak after spending most of the last month in Arlington Hospital.

But Dusek is secure, for now, though he says he never really worried about it much.

"I sure didn't think they'd just bring him (Curtis) in and drop me," Dusek said. "But let's face it, if I'm not performing like I should be, then they should put him in there if that's the best thing for the team.

"I thought it was a good move to get Mike. At the time, we were short at linebacker, and he's one of the best. He's the kind of veteran player George (Allen) likes, and he's done a great job considering he doesn't really know the system. He's a physical player, and he's going to help us."

Dusek has more important problems to ponder this week, namely, a St. Louis Cardinal offense that probably will be aimming its high-powered attack toward the left side where Dusek plays.

The Cardinals know that left end Ron McDole still has a sore right elbow. They also know that left cornerback Pat Fischer is hurting with a sore back, though it now appears he may be able to play. He participated in yesterday's closed practice, the first time this week he'd scrimmaged.

If Fisher cannot play, the Cardinals likely will try to take advantage of his replacement, second-year man Gerard Williams. So Dusek expects another frenetic afternoon Sunday.

The Cardinals also put opposing linebackers under great pressure because quarterback Jim Hart likes to throw to his running backs. In third-down passin gsituations. St. Louis often will use two speedy tailbacks. And if one of them is Terry Metcalf, the Redskins know their coverage had better be tight.

"I anticipate every play coming my way every week," said Dusek. "Having McDole in front of you and Fischer behind you is kind of nice, though. They've each got 17 years of experience, and after three years of playing with them, it makes the job a little easier."

DUsek says he has grown more comfortable at his position each week, that he reads defenses better and seldom hesitates as he did in 1975 when he first played the position fulltime.

That was the year Dusek, then 24, sent veteran Dave Robinson into retirement. Dusek became the youngest defensive player Allen had ever promoted to the Redskin's starting lineup.

"People don't remember Brad hardly ever played linebacker before he came with us," said defensive coordinator Torgy Torgeson." "He really does get better every week. His biggest attributes are his quickness and his toughness. He's got great intensity, and he hustles all over the field."

At 230 pounds, Dusek is one of the lightest NFL linebackers. "I think it's my metabolism," he said. "I just can't ever seem to get over 225. I just try and make up for it with quickness."

Dusek was swift enough to play safety, quarterback, flanker, fullback and tailback at Texas A&-M. And when the Redskins traded defensive tackle Donnell Smith to the Patriots in 1973 to acquire Dusek, a third-round pick that year, it may well have been one of the shrewdest deals Allen has made in Washington.

Offensive tackle George Starke said he cut his foot, and took the day off from practice. He said he would be able to play Sunday, and confirmed that he has signed a new contract with the club . . . Allen said rookie running back Clarence Harmon probably would be placed on the cab squad against the Cardinals because of a bad ankel sprain . . . Hanburger and Curtis again split the practice at right linebacker although Allen said he would nomake a decision on who will start until Sunday.