MEDINAH, ILL. -- Don't cheer yet, but the 90th U.S. Open, unlike many before it, may be won by a golfer who is entertaining as well as excellent, emotional as well as analytical, powerful as well as precise.

Someone like Tim Simpson, not Scott Simpson. Someone like Ian Woosnam or even Seve Ballesteros, not Hale Irwin.

Such optimism may be premature, but, due to good luck as much as good management, this Open actually may be concluded on an equitable golf course that gives the whole field a fighting chance. Torrential pre- tournament rains have softened and slowed the Medinah Country Club greens. And the rough was already stern, but sane. What is left is a long, honest, gorgeous test of golf.

That's why a fiendish flag- hunter like second-round leader Tim Simpson (135) -- whose hero was hell-for-leather Lanny Wadkins -- hasn't self- destructed. That's why Woosnam (140), the 5-foot-4 bomber who hits 320-yard drives, finds himself in the hunt despite a triple bogey. And that's why Ballesteros (142), who many said would never win an Open, calls the conditions, "Perfect. Could not be any better."

Normally, some straight-hitting, clean-living and tight-lipped medium-knocker who eats his spinach and never gambles enough to make a bogey wins this glamour title. Curtis Strange, Scott Simpson, Andy North, Larry Nelson, David Graham and Irwin have won eight of the last dozen.

Such straight arrows, of course, still litter the leader board. Jeff Sluman is a stroke behind Tim Simpson. Scott Simpson (Mr. Nice) and Irwin (the PGA Tour's Professor Emeritus of Nice) are tied for fifth.

Still, the U.S. Open, which has only had one what-the-hell victor since 1971 (Fuzzy Zoeller at Winged Foot in 1984) can hope for some variety.

Not that this would make the U.S. Golf Association happy.

The U.S. Open has a great and noble tradition. Reward rectitude, modesty, self-control, patience and analytical thinking. And do everything possible to penalyze intuitive, carefree, spontaneous genius. No long-hairs, no artistes, no free-thinking, touchy-feely players, no wild men -- please. Just as the Masters exists for golfers who are dominated by the right side of the brain, the U.S. Open was built for the left-siders.

If you are great in a determined, methodical way, like Jack Nicklaus, Ben Hogan or Strange, that's wonderful. But the USGA believes that sin must be punished -- always. The rough should be so high that a ball hit into it should cost a player one-half a stroke. And a computer analyzes every shot every year to make sure that this standard of punishment is preserved.

Unfortunately, some great players do not love a straight and cautious game. Some, like Sam Snead, Greg Norman and Woosnam, want to hit 300-yard drives. Some, like Arnold Palmer, Tom Watson and Ballesteros, possess magical powers of recovery that allow them to take chances, confident that they can still save par, or at worst, bogey. Some, like Ben Crenshaw and Nick Faldo, want to fire at the flag because they were born with special radar.

Those players have won a total of two U.S. Opens. By contrast, they've won 16 Masters and scores of important events. This, some believe, is not so much a commentary on them as the Open.

As Scott Simpson put it today, "Jack Nicklaus says that plodders do well in the U.S. Open. Well, a lot of those plodders are people I really admire, like Jack himself, Ben Hogan and Hale Irwin." A point perfectly taken. But variety is the spice of golf too.

For example, take Tim Simpson. Not a U.S. Open kind of guy. He used to be a notorious Tour crab. Once, he tried to punch a heckler through a car window. Just last month, he got into it with a loudmouth in Atlanta. He's spent eight years working with a sports psychologist trying not to take golf and himself so seriously. It's working. But he's still got an edge. After only one top-30 season (in '89) and three career wins in 14, he thinks he should be much better known. Now that's cocky.

Simpson likes to hunt white-tailed deer with either bow or rifle. And he volunteers "the biggest game I ever bagged was my Sicilian wife."

In addition, Simpson doesn't talk like a U.S. Open winner. More like a publinx winner. "Made a 40-footer. What a bomb." "Knocked it 108 yards through the branches, dead on the flag. God knows how I did that." "Best pitch I've made in months."

Most U.S. Open winners are diligent, industrious types, like Irwin, who has taken time off from building 10 golf courses to try to win his third Open. Simpson shrugs and says, "I can't see myself hangin' around in my fifties. I want to watch my children grow up. . . . How much money is enough? Another million? Then another million?"

The U.S. Open may not be ready for a champion who sings the praises of laziness and early retirement, and who thinks that an extra million dollars in the bank isn't such a big deal. To win this event, you're supposed to grind and grimmace as though golf were life and victory were a proof of character. Don't sell that theory to this Open's leader. Simpson says he never started to get his life in order, and play better golf, until his daughter (now healthy) almost died at birth four years ago. That "slap in the face" began the unraveling of his obsessions with golf and himself.

By Sunday, if the sun and wind have their way and the rains do not return, this course may be a purgatory for belters like Woosnam, predators like Tim Simpson and imaginative golf artists like Ballesteros. Maybe par-par-par will be the order of the day, as it's always been.

Still, we can hope for conditions that allow Tim Simpson, and others, to play with some freedom.

Normally, such a sensible strategy would be a prescription for suicide on Sunday in the U.S. Open. Moderation is almost never good enough. Only utter straitjacketed caution -- middle of the fairway, middle of the green, keep everything below the hole and never try to make a putt longer than a few feet -- wins this ultraconservative prize.

But maybe not this time.