Some of the Redskins' offensive notions have changed dramatically in a year. This is now a one-back, two-tight-end team, with Joe Washington the featured runner. Terry Metcalf is a receiver, not a halfback, and the line no longer is a question mark.

But one question has not changed: Where does Wilbur Jackson fit in?

Last summer, the return of John Riggins and the acquisition of Metcalf and Washington pushed Jackson so deep into the background that not even his fine training camp play could earn him a starting position.

Still, three games into the season, Jackson was on the verge of relegating Riggins to spot duty. With Washington hurt and Riggins playing poorly, Jackson gained 104 yards against St. Louis and then 96 in the first half against Philadelphia before hurting his knee.

That Eagle game was the last time Jackson would carry the ball in 1981. The ligament damage to his knee, considered minor at first, limited him to one brief appearance as a special teams performer against Detroit before he was placed on injured reserve.

In his absence, the Redskins went back to Riggins, who performed solidly, mainly in short-yardage situations. Riggins had one 100-yard game and scored a career-best 13 touchdowns, tying him for the National Football Conference lead.

Now the Redskins know how they want to use Riggins, in what Coach Joe Gibbs calls power situations. But that does not necessarily mean that Jackson will be on the sidelines, the coaches forgetting what he did for the team last year.

Even though he is a fullback, Jackson runs more like a halfback. His style is closer to Washington's than Riggins'. And he is considered by the Redskins to be better suited than Riggins to play in a one-back offense, where a cut-back, darting technique is more successful than Riggins' straight-ahead surges.

Since the Redskins don't have a halfback as quick as Washington, Jackson would be a likely replacement in case Washington were injured. Gibbs goes even further.

"Wilbur has a chance to be a starting back (along with Washington)," he said. "You can't forget how he was running those two games before he got hurt. He did a lot of great things. He may be our best all-around runner and he certainly helps himself by the way he can play special teams.

"What Wilbur has to do is show he can hold onto the ball and show he can go through a season without getting hurt."

Jackson, who is beginning his ninth season in the league and third with Washington, had knee troubles in 1978 as well as last season, but says he has been healthy otherwise throughout his college and pro career.

"I really don't consider myself injury prone," he said. "Anybody who plays long enough is going to get hurt. It happens to all of us. You just hope to avoid the long-term injuries."

But the Redskins believe something can be done about Jackson's fumbling.

"We want him to carry the ball higher . . . get it into the rib-cage area," said Don Breaux, the running back coach.

"We are going to emphasize it every day. Maybe where he carries the ball has nothing to do with the fumbling, but it's a start."

Jackson: "Until someone brings it up, I don't even think about fumbles. I didn't think I had a fumbler's reputation. But they are worried about it and I'm going to work at getting it away from my hip and up higher. It's just always felt more comfortable lower."

Gibbs, however, is paranoid about fumbles, since mistakes proved so costly to the Redskins early last year. And neither Riggins nor Washington fumbled much the last half of the season, when the Redskins won eight of their final 11 games.

Jackson's unsettled situation has been characteristic of his short Redskin career. In 1979, when he was obtained from San Francisco for two No. 2 choices, he was switched from fullback to halfback, despite the fact he had been acquired to replace the then-retired Riggins.

"My knee feels good, I don't think about it anymore when I'm out there," said Jackson, who avoided offseason surgery. "I've been doing a lot of running and I'm coming in here in good shape . . .

"Everyone knows playing time is limited with one back," said Jackson. "But there is another side, too. You also realize you don't have to conserve anything when you are in there. You can go all out every time and then get some rest."

At times last year, the Redskins were reluctant to consider resting Washington. That could change if Jackson can regain his 1981 form. And a more rested Washington would be an added boost to Gibbs' offense.