Walter Payton is the brightest, most mysterious UFO in the NFL sky. The Chicago Bear running back, who broke pro football's rushing record Sunday with 275 yards, does not enjoy close encounters of any kind.

On the field, where he rambles with extrasensory abandon, and off it, where he sometimes walks a city block on his hands on an acrobatic whim, Payton cultivates the aura of a shy enigmatic alien.

"'Sweetness' is really a weird individual" says Bearguard Noah Jackson using Payton's unique nickname. "He just won't let you get to know anything about him!" "I don't think anyone can understand me, really," Payton says, gringing. "It's an imposible task."

Payton's place is onthe field. Buteven there is has taken him an almost unconscionablylong time to get his due. A running back's time is short. Today's unidentified flying object quickly object quickly becomes an injured and ground craft in the NFL. Payton holds the NCAA career scoring record of 464 points at Jacksson (Miss) state, but few know it. He scored 66 collegiate touchdowns, kicked field goals and extra points, punted, completed 14 option passes and returned kickoffs an incredible average of 43 yard

Yet, because he played at an all-black SWAC school, Payton finished far behind Archie Griffin and Anthony Davis in the national publicity sweepstakes."

"I'm the best running back in the draft," blurted the normally humble Payton in 1974, and Griffin and Davis know it. When I get through with Chicago, they're going to love me."

Fans far from Chicago might love Payton if only they knew him better. Indeed, Payton is a complete contrast to the man with whom he is now inevitably compared O. J. Simpson.

Where Simpson is wholesome as orange juice, cheerful and open as California Payton can turn as chill as Chicago's North Side or seem as convoluted as The Loon.

Simpson's running style is breathtaking, but easy to comprehend: mix speed, size and power with a gliding stride and an unequaled ability to shift gears and directions in the open field-that's O.J.

Payton is harder to understand, and thus poem. Payton is lurching, unpredictable free verse - an acquired taste.

The 23-year-old Bear will burst into a thicket of bodies - one Simpson might eschew -only to pop out unaccountably or the other side without a thorn in his side.

Where Simpson might absorb a loss meekly, Payton treats every tackle as an insult.

"Sooner or later, I'll break one." Simpson says.

"I'm a never-say-die runner," Payton counters.

Like a larger, more naturally gifted Larry Brown, Payton makes every five-yard gain a probing, arrogant adventure as he smashes and bounces along the line trying to rip and lunge for every yard.

"Payton." Simpson says with respect, "is one of the insane runners."

"Let's say," laughs Payton, "my motto is: "Whatever it takes.'"

Payton must run for 600 yards in a season. The 5-foot-10, 210-pound Bear has 1,404 yeard in 10 games, but with four losing teams left on the Chicago schedule (Detroit, Tampa Bay, Green Bay and New York Giants), he may be able to produce the 150-yard average he needs to squeeze O. J.

Payton seems unmoved by records and less than obsessed by the limelight. He hands the ball to his linemen to spike in the end zone and confines himself to an occasional jubilant back flip.

Before Sunday's shredding of the Minnesota defense, Payton has missed parts of two practices because of "hot and cold flashes" caused by flu. "I didn't know whether I'd make it through the introductions," he said afterward.

Yet with each carry he became stronger, just as a guest from the far reaches of outer space might be expected to do. With three minutes to play he broke a 58-yard run.

"I had 40 caries?" he asked. "It felt like 20."

True to his image as a gridiron gunslinger, a tight-lipped Man With No Name. Payton kenw nothing of his statistics during the record-setting game. He forbids anyone to speak to him or break his concentration from first whistle to final gun. "I can't stand to be talked to during a game," he say. "Never."

The voice is soft, high-pitched and almost gentle. The words seem more harsh and incisive when they are written down.

In just two days, as though by plan, Payton will have a national TV audience when the Bears meet the Lions Thanksgiving Day.

Payton was asked yesterday what the Lions could do to put a halt to a man who has ripped off games of 275, 192 and 205 yards in the last month.

"The night before the game," said Payton, the notion coming to him as unexpectedly as an intuitive cutback against the grain. "I guess they'd have to kidnap me."

If they could get close enough.