When Seve Ballesteros strode to the tee at the short, sharply doglegged par-4 17th hole today and yanked out a driver, his sizable gallery buzzed with anticipation. When he suddenly turned 180 degrees and teed the ball up, the crowd got close to giddy. There was a more inviting target this practice round than a green merely 322 yards away; he was going to drive the nearby Allegheny River.

So he can't smack a golf ball three miles after all.

So he can't even hit it 800 or so yards to an island he later said had been the intended landing area.

Some others here for the U.S. Open aren't sure Ballesteros could not walk across the Allegheny to where the ball plopped in, somehow hack it back to dry land and still make par at 17. The world's hottest golfer at the moment has some fine players quaking in their cleats. And some splendid ones being close to deferential.

"Right now," said Johnny Miller, "he's the best player in the game. And he will be for the next several years, if his back doesn't go out."

Arnold Palmer was astonished that anyone as good as Miller, who shot 63 in the final round and won the Open here 10 years ago, would admit such a thing. Still, Palmer allowed: "Seve has all the ingredients (to dominate golf for at least a brief period); it's just a matter of time."

"I think Seve's about ready to win a U.S. Open," said defending champion Tom Watson.

Already, at age 26, Ballesteros has won one more of the traditional major tournaments than Miller. And his two Masters championships and one British Open title are three more than have been mustered by the herd of Kites and Crenshaws, Lietzkes, Beans and Morgans, who have been at their craft much longer.

Having won his second Masters in April, Ballesteros is the only player here who can be pestered about the slam, his chances of also winning the U.S. Open, the British Open and the PGA in the same year. He gives such questions the sort of half-laugh they deserve.

"You have to win the first three before you can start talking about a slam," he added. "It's not impossible, but it's almost impossible."

But that's exactly the charm of Ballesteros: he turns the impossible into par. He makes birdie from parking lots, 3s from under trees, eagles with a tournament on the line.

The three-iron he hit on the 72nd hole at Westchester Sunday sort of Seveized his peers. And added to his immense charm for duffers outside the ropes. He hit the ball closer to Vermont than some of the pins that final round. But when the pressure vise grew tightest, he responded with two exquisite shots. Needing birdie to win, he made eagle.

Miller said Ballesteros insists he is in near-total peace when he stands on the first tee just before the final round of a tournament he is leading. To illustrate this, Ballesteros boasts of being able to hold a golf ball at such moments in a circle formed by the thumb and index finger and then balancing another ball on top.

Most of us would trip over the ball washer.

Whether he will get to show this stunt Sunday is arguable. Although he has won his two most recent tournaments in the United States and also is coming off victory in the British PGA, Ballesteros has not done well in our national open. From 1978 on, he has tied for 16th, missed the cut, been disqualified for missing his tee time, tied for 41st and missed the cut.

He never saw Oakmont before today.

He can play it as few others.

"Seve hits one-irons as far as, say, Hubert Green hits a driver," said Greg Norman. "Seve hits one-irons as far as 70 percent of the players out here hit drivers."

That will be his strategy when the tournament gets serious Thursday. No more fun swings toward islands. Unless the wind and pin placements conspire charitably, Ballesteros will regularly use that one-iron off the tee. He hit it 23 times at Westchester.

"I'll use it on all the par-4s," he said. Somebody mentioned 17, which breaks severely enough left that long-ball gamblers have driven it and made one-putt eagles.

"Unless it's downwind and the pin's in the back," he said, "I'll lay up."

No silly shows this week. Ballesteros has history in mind.

"You have to think very much on this course," he said. "You must be very smart."

And strong. And inventive.

When he is straight, Ballesteros is supreme; his wild streaks are what intrigue duffers, when he is out there an acre from the fairway in what Miller calls "Seve rough." From 100 yards on in, from inside bird's bedrooms, from fairway traps where one foot is one foot higher than the other, he is a fascinating artist. Ballesteros can hit bunker shots with three-irons as accurately as many pros using sand wedges.

"Greatest pair of hands in the game of golf," Norman said. "His chip shots are sort of freakish. Even other pros talk about his being wild off the tee. Yet he only hit three bad tee shots at Augusta. That's all anyone talked about, though."

Still, we have visited Ballesteros in golfing jail--and seen him escape. Even he admits: "I have a good imagination with shots. Anytime I can swing the club, I can put the ball about where I want it. I believe very much in myself."

Of all the maximum-security pens from which Ballesteros has sprung, none was more pleasing than on the final hole of the '76 British Open. That is when he first burst into the international big time, as a Spanish teen-ager scrambling all over Royal Birkdale.

"I wasn't very far from the green (on the par-5 final hole)," he recalled. "But I was in the deep rough. The flag was cut near the part of the green closest to me, and the green itself was sloping away from me. So I hit a nine-iron into a tiny opening (of rough) between two traps and the ball stopped four feet from the cup.

"I made the birdie putt to tie Jack Nicklaus for second place."

He's been impressing his elite elders ever since.