He looks like a little boy on Christmas morning who has jumped into an oversized football uniform Santa Claus brought him.

His helmet looks too big as his eyes peer out from the large face mask, thick, bulky hip pads.

But then the game starts. And the undersized kid in the oversized uniform becomes Tony Dorsett.

He has been overshadowed this season by the likes of Chicago's Walter Payton and didn't even make the Cowboys' starting lineup until last week, but his potential is mind boggling.

Now, a knee injury threatens to sideline him before his second scheduled start Sunday in Washington against the Redskins. But it hasn't dampened his spirits.

Dorsett injured his right knee in practice Wednesday and was unable to work out today and will be held out of practice again Friday. He will try to work out lightly Saturday.

"If the healing process continues like it has. I'll play," he said. "It's a lot better now than I thought it would be."

Football fans and experts will argue into overtime over who is the best running back of all time. But there is little argument about the top four: Jim Brown, Gale Sayers, O.J. Simpson and Payton.

Dorsett might end up having been more effective for more seasons and having won more championships than any of them.

He is working with an advantage that they lacked in varying degress: Dorsett makes his team better, but he is not the franchise. He has help and a lot of it, both in the Cowboys' personnel and in the way Dallas uses him.

He is used as a tailback in the I formation a setback in a split backfield, a slotback in the shotgun and he goes in motion at times. He is not run into the ground.

"If you take Payton cut of Chicago's offense, Chicago doesn't have an offense anymore." Dorsett said. "If you take me out of our offense, we still have one. Preston (Pearson) or someone else will step in and keep on rolling."

Until last week when he played virtually the whole game against Pittsburgh. Dorsett was playing only about half a game, but still scaring Cowboy opponents.

He came into the league ready to burn it up and even predicted he would gain 1,500 yards as a rookie. He says now that was not the most intelligent thing he's ever done.

"There's no one who can meet up to Payton right now, and I know that as well as anybody," Dorsett said. "But I'm patient, my day will come.

"I was brought along nice and slow. I thought I would pick up the system faster than I did, but I just didn't. I didn't get in the books like I should have. I finally got myself together and now things are becoming second nature to me. I'm comfortable."

No one could be much more comfortable with Dorsett than Dallas quarterback Roger Staubach. He says that teams are so keyed to stop Dorsett that the passing game is left wide open.

"Last year," said Staubach, "we couldn't run the ball and we were doing such things as passing on third down and two against Los Angeles in the playoffs. We don't have to do that anymore."

One of the reasons Dorsett could be brought along slowly is Pearson. He was the starter last year and coach Tom Landry had Dorsett complete with Pearson for the starting job. Pearson won.

But the incumbent running back said it was only a matter of time before Dorsett got into the starting lineup.

"He's a great runner," Pearson said, "and he'll get better. He's got more explosive quickness than any back I've ever seen. O.J. Simpson had hie speed, but not his quickness. He just had to learn that there was more to this league than running with the ball. He had done that now."

One doesn't have to look at Dorsett very long to realize his enormous talent. He sets up blockers by loping and once the block is made, he bursts through a hole.

"I saw his ability when he was running routes against linebackers on the first day he worked out in Dallas, about six weeks before training camp," said offensive back coach Dan Reeves. "He was getting open without using fakes. He would just accelerate away from them."

The more reserved Landry simply says, "Dorsett is going to be great . . . if he stays heaithy,"

This is the second time Dorsett has been injured, neither has been serious. He missed 10 days of training camp and was at less than full speed for about a month when he bruised his other knee.

"When he grows more familiar with our offense and learns how to hit the seam right, he's going to run up a lot of yards," Landry said. "We're not putting him in the open as well as we will later on."

So the man who says he was afraid of contact when he was a youngster, but who went on to gain 6,082 yeards at the University of Pittsburgh and win the Heisman Trophy, is the biggest thing to hit Dallas since the Cowboy cheerleaders.

His first love is hot football, but his 4-year-old son, Anthony Jr., or Little Hawk. The child lives with his mother, whom Dorsett never married, in West Virginia, Dorsett brings him down to Dallas often and devotes much of his time to him.

Dorsett does some promotional work for Rawlings Sporting Goods and Converse Shoes and is working "on something big with Brut.

"I don't want to overendorse myself," he said. "I never have. I'm still basically the same person I've always been, the same simple old me. I've just quiet person I was before high school."

Until he touches a football.