She stood under the trees for a moment, not trying to hide form the afternoon sun, just figuring how she would play her next shot. Debbie Massey had made similar calculations before she began the ninth hole today. She would make more before she finished the third round of the United States Women's Open.

This time, however, she had to be careful. Her ball was between a couple of trees and Massey didn't want to be too strong coming out. If she was, there was a good chance her ball would hit the green and roll above the hole. "And that's one place you don't want to be," Massey said.

So Massey played the ball just short of the green, just where she wanted to be. Her pitch landed 20 feet above the hole, just where she didn't want to be. She made the putt. "I scrambled my brains out," Massey said.

And probably Sally Little's brains, too. Little had the misfortune of playing with Massey today. When Little hit in the fairway, Massey would land in the rough. When Little would be on the green, Massey would be pulling out the sand wedge. Not that Massey noticed such things. Or that she saw what they leader board at Brooklawn Country Club read.

"I was too busy," she said. "I didn't have much time."

Sunday might be different. At least before she begins playing the final round, right before the Open goes into the living rooms and grill rooms of America (4:30 p.m., WJLA-TV-7). Then, Massey will see her name on top of the board, one under, in front of the pack, three shots ahead of Jerilyn Britz. Not that it will matter to Massey. "Three shots is nothing," she said. "It's easy to make up. It's easy to lose, too."

Which Massey did today and hopes not to do Sunday. The swing in the third round really was five shots, from the time Britz began at two-under and Massey went to one-over after two holes to when Britz finished bogey-bogey - 75. The difference with Little was four shots, from the time she went one-under with a birdie on No. 5 to her bogey and double bogey on Nos. 13 and 15. Little finished at 74 and, with former Open champions Sandra Palmer (1975) and Susie Berning (68 71 72) is four shots back.

"It may be more difficult to make up strokes on this course than other Open courses," Palmer said. "I think somebody's going to have to make some mistakes. The trouble is, Debbie is not the kind of player who makes mistakes."

At least not the kind which she can't extricate herself from, the kind she made today, over and over again. There was a misplayed approach shot on the first hole, which landed in the trap. In that instance, Massey made a four-foot-putt to save par. There was the 20-footer on No. 9. There was a shot through the trees on No. 17, which again landed in the trap, and a 12-footer to save par. "I hit a lot of bad shots," Massey said.

Others who did the same, but were not as fortunate, were Nancy Lopez and Hollis Stacy, who have attracted most of the attention from the record crowds here. They started with the lines by the first tee standing five deep and their scores reading four-over. Lopez took bogeys on the first two holes, birdied No. 5 but never got closer, finishing for the third straight day at 73. Stack bogeyed Nos. 4 and 6. She, too, could not make a run, finishing at 74-220.

"I want to make putts but I don't feel confident going for them," Lopez said. "There are times when I play the breaks right and they break wrong and there are time when I play the breaks wrong and they go right. It's frustrating."

Perhaps, but surely not as frustrating as it has been for Stacy. She won the last two Opens and was seemingly headed for a record third. She won last week in Indiana and she was full of confidence. But that was before the heat got to her head and the greens had got to game. "It's been a long week," Stacy said.

For Debbie Massey, it is her time on center stage.

"It's exciting," she said.