Slowly, Wilbur Jackson walked onto the Redskin practice field. He seemed hesitant, lost, like a little boy hoping the big boys ask him to play. He carried a helmet (it hadn't been painted with a number yet) at his side, hooking the face mask with two fingers. In shorts and T-shirts, this was the Redskins' last practice in town. And here, at last, came Hope.

"Wilbur," someone said, and Jackson looked to his right. "I'm Joe Walton, how are you?" The Redskins' offensive coordinator knows Hope when he sees it, and in Wilbur Jackson he sees the Redskins' best chance at making something of this season.

Words of welcome passed between the men, but only for a second because now Joe Theismann, the quarterback, was holding a finger up for Jackson. "On one," Theisman said. Jackson nodded in understanding, for with Walton and backfield coach Fred O'Connor watching, it was time for the newest Redskin to go to work.

He would learn to recognize Joe Theisann's signal-calling cadence. With Jackson standing behind him, helmet in hand, Theisman moved under center Bob Kuziel and barked out, "Two, twenty-five . . . Two, twenty-five . . . Hut."

Kuziel pounded the ball into Theismann's hands and the quarterback turned to Jackson. The big fullback nodded. Three minutes later, his helmet tossed aside, Wilbur Jackson came from a three-point stance to take a handoff from Theismann.

Only flukes win in the National Football League without a great ball-carrier. San Diego did it last year for a while by filling the sky with Dan Fouts passes, and Denver did it for a while with extraordinary defense. Miami did it because Don Shula is a brilliant coach who found a way to get a deteriorating Larry Csonka over 800 yards. But each team lost in the first round of the playoffs.

John Riggins quit the Redskins six weeks ago, demanding to renegotiate the option year of the contract he agreed to six years ago. That left the Redskins with running backs unlikely to gain as much as 600 yards in a season. rIt also left them with running backs unlikely to gain 100 yards.

So the team was forced into a trade. It gave up two No. 2 draft choices to get Jackson from the San Francisco 49ers, where in five seasons' work he had gained more than 700 yards three times. At 28, soon to be 29, only two years removed from a knee injury that forced him to sit out the 1978 season, his job apparently to be taken soon by a rookie of promise -- Wilbur Jackson now comes to the Redskins not as a diminished veteran but as Hope.

Jackson doesn't know it.

"I just want to come in and contribute," he said today.

He knows nothing about the Riggins affair.

"They told me some about it today, but other than that I don't know anything. Maybe I read it in the newspaper once."

Someone asked if the knee ever bothered him now.

"I never had knee surgery," Jackson said, although the 49ers press guide and Bobby Beathard, the Redskins general manager, say surgery was done in 1978.

"All they did was an arthroscope," Jackson said. "They use this scope to look in the knee and see if it needs surgery. There were ligaments torn, but they didn't need surgery. They put it in a cast for three months. I was hurt in the second preseason game that year and I didn't run again until February."

Jackson said the knee is to blame, indirectly and only in part, for his mediocre 375 yards rushing last season. The 49ers' offensive line wasn't so hot, either, and in desperation to recover from their defensive mistakes, the 49ers threw more passes than any team in the NFL (602, which is 53 more than San Diego launched).

"The 375 yards is misleading," he said when someone asked if he is a better runner than he showed in 1979. "Sitting out that year with my knee caused me, I think to worry about it last year.I didn't think it would, but it did.

"I may have lost some self-confidence. Subsconsciously, it may have worried me."

And now?

"I'm looking forward to playing with the Redskins."

What kind of back will he be?

"I like to run inside the tackles, but I have enough speed to get outside. Basically, I'm a fullback. And I block fairly well and I can catch the ball fairly well."

What Jackson hopes for most, and what the Redskins would dearly love, is to again learn how to win.

He forgot in San Francisco how sweet victory is, how sweet it had been in his three seasons at Alabama. What Alabama did was whip up on somebody new every Saturday, as it always had. Wilbur Jackson, growing up in Ozark, a couple hundred miles from Tuscaloosa, always watched the Tide on TV.

He never thought much about playing for Bear Bryant. He was good enough. He was a three-sport star at Carroll high. But Wilbur Jackson never thought about playing at Alabama because in 1970 no black played at Alabama. He was, in 1971, the first.

"Everyone helped me out, from Coach Bryant on," Jackson said. "I had no problems."

He averaged 7.2 yards a carry for Alabama, although the Tide's over-whelming depth limited his three-year total to only 212 carries. What Alabama did was win: 11-1, 10-2 and 11-1 with three league championships and one national championship.

As dazzling as those years were, Jackson's pro years have been numbing. The 49ers have gone 6-8, 5-9, 8-6, 5-9 and 2-14 with Jackson.

"You win so much you expect to win," he said of his Alabama days, adding to his 46er trials, "It's hard to try to win again. Losing can get to be habit forming." Jack Pardee, the Redskin coach, also played for Bear Bryant, as he reminded Jackson five minutes after he arrived here today.

Pardee said he wanted to get Jackson going right away. Team meeting. Films. The no pads practice.

"And then," Pardee said, "you'll play three quarters Saturday night."

They both laughed at what the Bear had taught them.