The Redskins obtained veteran fullback Wilbur Jackson, a 1974 first-round draft choice, from the San Francisco 49ers today in an attempt to fill the void created by John Riggins' absence from training camp.

But the price was steep. League sources say Washington had to give up two No. 2 draft picks, one in the 1981 draft one in 1982, before the 49ers would part with Jackson, 28, their starting fullback this preseason.

The Redskins see the trade as their way of telling Riggins, who is holding out until the club renegotiates the 1981 option year of his contract, that they are determined to play this season without him if necessary.

But Riggins, speaking today from his home in Lawrence, Kan., said he didn't view the trade as a means of forcing him to change his mind. And while he said he still believed strongly in his holdout, he revealed for the first time the possibility he might want to play in 1981 even if he sits out this season.

"Maybe I'll find out I miss the game more than I think," he said. "And maybe I'll change my mind this year. I'm not saying I won't I'm that impulsive. Who knows what I'll do tomorrow?"

Riggins, who says he thinks about returning "once or twice every day." said he didn't see why a team always "had to be the one to tell a player he was through. Why can't a player tell the team?

"I think about what happen to Billy Kilmer and Jake Scott and Ron McDole and Chris Hanburger and Harold McLinton. I don't think the Redskins thought much about them. They just told them they were through, period.

"I'm just trying to protect myself from that. I like success but maybe I'm still a little scared of it . . . I'm at the top of my game now. I don't want to become yesterday's hero."

General Manager Bobby Beathard, who finalized the Jackson deal with a series of phone calls starting at 1:30 this morning, refused to comment on the choices the Redskins gave up, but insisted no first-round selections were involved.

"I don't think we had to pay a ransom for him," Beathard said, "But we were in a position where we had to get somebody. If John was in camp and we were interested in Wilbur, the price we might have paid would have been lower."

Although he may not start immediately, Jackson, who had knee surgery two years ago, is being projected as the No. 1 fullback. That would allow Clarence Harmon to return to his role as third-down and pass-receiving specialist.

"I certainly hope that he can fill the role that Riggins filled," Coach Jack Pardee said. "That would keep Clarence free for the role he played last year. We didn't think Clarence could fill both roles. We'd rather use him where he is so successful."

But Harmon still considers himself the No. 1 fullback, the spot he has filled since Riggins left camp. "I haven't been told anything different," he said. "But I do what they want me to do. I only work here. I'll go back to third downs."

Said Jo Walton, offensive coordinator, "You keep your .300 hitter (Harmon) batting third. That's the smart thing to do. But we'll have to see how Wilbur works out before we can determine who plays when. We'll see how fast, he catches on."

Washington had little choice but to make a deal, since it was becoming apparent Riggins was settling in for a long holdout over his demands for a one-year, $500,000 guaranteed pact in 1981. Without him, the Redskins were left with Harmon, a gifted player who does not fill their need for a big back, and backups Don Testerman and rookie Rickey Claitt.

"The trade got us out of a very, very vulnerable position," Pardee said. "Now we are in a more normal position. We were really exposed to injury and fatigue with Clarence. We couldn't risk having him hurt and not knowing what else we would get out of that position.

"Wilbur can step in right away and help up. He is a proven back. We don't need three or four years to develop him."

Jackson is 10 pounds lighter than Riggins (220 to 230); and is not nearly as strong, considered quicker and a better pass receiver. He caught 53 passes last season, but gained only 375 rushing yards. However, San Francisco relied almost entirely on its passing game.

Previously, Jackson had three seasons of more than 700 yards rushing, including a career-high 792 in 1976.He has gained 2,955 yards and caught 149 passes in his career. He missed the entire 1978 season while recovering from knee surgery, but played all of last year.

"He gives us the big back we have needed," Walton said. "I'm excited about getting him. He can do a lot of things well. He's a quality back and he should help us."

Beathard said Jackson was having a "really tremendous training camp, which was one reason we had a hard time getting him. They were very reluctant to let him go. But they drafted a fullback, Earl Cooper, No. 1 and they think he can do the job."

Jackson said he wasn't shocked by the trade, since rumors involving him in deals "had been running around all along. At least I'm going to a good club and I'll be closer to my home in Alabama."

Beathard checked out Jackson's knees three weeks ago while watching him in person at a 49er camp workout. The Redskins were impressed when Jackson caught a 48-yard touchdown pass against Dan Diego last week.

Still Beathard went to bed Wednesday night certain he would not obtain Jackson any time soon, at least not before further negotiations with San Francisco.

"Right from the beginning, they were realistic in their demands," he said. "But they were asking too much. I made a new offer to them Wednesday. sI was driving to Carlisle from Redskin Park and stopping at pay phones along the way to talk to them. This person got into one booth for 10 minutes at one point and I thought I had blown the deal.

"But finally, they said they would get back to me Wednesday night by midnight. When they didn't, I went to bed."

At 1 a.m. Thursday morning, the 49ers woke up Beathard, telling him they were interested in further talks. They negotiated and Beathard made yet another offer, the one the 49ers finally accepted.

"They called me later this morning and I felt for sure they were calling it off. They really like him and he was playing so good in camp. But they took the offer.I was really happy how it worked out.

"You hate to give up a draft choices, but really, next year isn't a good draft year, so giving up a high choice doesn't hurt too much. And we are in good shape in 1982 except for this choice and for one other." That latter choice, sources say, is a medium-round pick that goes to Pittsburgh for quarterback Mike Kruczek.

Beathard said the Redskins "are not getting into the draft choice trading business. This was a unique situation, we didn't have many alternatives. But we aren't going to give up on No. 1s."

Added Pardee: "If Wilbur works out, then he is worth what we gave up. We'd be using the choices for runnign backs probably, anyway. Here, we have someone we know can play."

Both officials said the trade does not close the door on a return by Riggins. "We'd love to have him back." Pardee said. "It just means we can go about our business better now without him. We've got a season-opener coming-up. That's what we have to concentrate on."

In Kansas, Riggins said he felt the trade was not really a slap at him but rather "it reflected on Don Testerman and whoever else they have running with Clarence at fullback. It doesn't affect me. Maybe it should, but right now it doesn't."

The Redskins made room for Jackson on the roster by dropping offensive tackle Greg Dubinetz. Dubinetz was a backup tackle last year but was outplayed in camp by veteran Mike Gibbons and rookie Jerry Scanlan . . . Jackson is expected to appear in Carlisle Friday morning and take part in the last practice of training camp Friday afternoon. He is not expected to play Saturday against Oakland.