Ten days before the season opener with Dallas, Redskin Coach Joe Gibbs is trying to sort out his running back situation, mainly due to Wilbur Jackson's unexpected fine play during the last part of training camp.

As well as Terry Metcalf, Joe Washington and John Riggins have played this summer, Jackson has performed better. How does Gibbs best utilize these backs, especially Jackson, who probably has earned equal playing time at fullback with Riggins?

"I honestly can say that I don't know for sure how we are going to do it," Gibbs said. "For now, we probably will be alternating those four guys until we get a better feel. We want to do our best to keep them rolling. It's not a bad problem to have. I think it's a plus. Our running situation is really solid. I feel good about it."

Will Riggins and Washington start against Dallas?

"I really don't know," Gibbs said. "We've been alternating all four of them during preseason. I know coaches will say all four are starters, but I think we are going to try to treat all them equally. We have to find out, for example, who needs to play more to get in the groove better, that type of thing. It would be to the team's benefit to keep them all fresh in every game."

And despite appearances, Gibbs says he has not forgotten about Clarence Harmon, the club's most dependable back in pressure situations the past few years. Harmon has played very little, except on special teams, during the first three preseason games, but Gibbs said his talents will be fully employed on offense.

"I see Clarence as our fullback on third-and-long passing situations," Gibbs said. "And he'll be used in the two-minute periods just like all our backs. With all the backs we were trying to look at until now, he's sort of been lost in the shuffle, but we aren't ignoring him.

"Besides, he's got a lot of special teams duties, he's really the captain now and has a lot of responsibility that way."

Although Riggins probably will start against Dallas at RFK Stadium, no one rules out the possibility that another outstanding showing by Jackson in the final preseason game Sunday at New England could earn him top fullback billing.

He's probably our most productive back right now," Gibbs said of Jackson, who has gained 50 more yards (119) than any other Redskin in preseason."Even against Baltimore, when no one was really doing anything, Wilbur ran really well. He's showing good quickness and dependability."

With the return of Riggins, the addition of Washington and Metcalf and the presence of Harmon, it appeared that Jackson's playing time this season would be severely limited, especially after his fumbling problems at the end of the 1980 schedule. Even though he led the team in rushing (708 yards) he wound up playing behind Bobby Hammond the final game last year, a spot he said yesterday he deserved "with the way I was playing."

When riggins quickly showed that a year's layoff hadn't bothered him, and Metcalf and Washington looked sharp early, Jackson became lost in the shuffle. And that's where most observers probably expected him to stay the rest of the season.

Instead, his play so far is one of the more remarkable stories of an already intriguing training camp. The key was Gibb's decision to return him to fullback; injuries forced Jack Pardee to use him at halfback. The change has made him much more comfortable. He is now playing more like the running back General Manager Bobby Beathard thought he was obtaining when he gave up two second-round draft choices to San Francisco last summer to fill the void left by Riggins' walkout over a contract dispute.

"I feel good about the way I'm running, but I'm not that happy with my blocking," said Jackson, one of the quietest, most likable Redskin players. "I thought I was a good blocker, but I've been having my troubles this camp. And I'm not always doing the same thing wrong.

"It helps to settle into one position, whether it's halfback or fullback. I've played both in camp, but mostly fullback. I just came in here with the attitude that I would play as hard as I could and do the best job I could and then they would determine what to do with me. I didn't spend much time thinking about who else was around."

Nor did he spend much time thinking about his fumbling problems at the end of last season. "The same thing happened once before in my career and the next season, I was okay. The same thing is going on now. I haven't had any problems so far, I feel great. It's really a mystery to me."

Although Jackson has never gained more than 1,000 yards in a season (his best is 792), he also never has played on a very good team. During his 49er years, that team struggled and last season, the Redskins were woeful. Still, he caught 53 passes in 1979 and 27 in 1980, and remains a better receiver than Riggins.

"I think it shows something about wilbur the way he has performed this camp," Beathard said."He just goes about his business and never says a word. Some people might have given up. Instead, I've never seen him look better."

Jackson's emergence probably has cut into Harmon's playing time. But Harmon, the easygoing fisherman from Kosciusko, Miss., says he feels comfortable performing "most of the same duties I had in 1979" even after a full dose as a starter last year, when he ran for 484 yards (second to Jackson) caught 54 passes (second to Art Monk) and scored eight touchdowns, highest on the club.

"Not that I didn't like being a starter," he said, "but they are signing my paycheck and I'll do whatever they want. I'm plenty busy. I caught a lot of passes (32) playing third downs in 1979. And with all the young people on the special teams, I've been trying to help them out. Last Saturday, I spent a lot of time getting them in the right spots and all.

"The last thing Dallas Hickman (former special teams captain) told me last week when he was cut was, 'Keep the Wild Bunch going.' I like that responsibility. But I think I'll be playing a lot in the offense, too. I sure hope so, at least."