Third-seeded Andrea Jaeger and fifth-seeded Pam Shriver were defeated in straight sets yesterday at Smith Center as upsets continued in the Avon Championships of Washington.

Jaeger was defeated, 6-3, 7-6 (7-5), by Barbara Potter, who ousted top-seeded Tracy Austin earlier in the tournament. Anne Smith defeated Shriver, 6-3, 6-4.

Among the seeds, only No. 2 Martina Navratilova, who routed Bettina Bunge, the sixth seed, 6-1, 6-2, and No. 4 Sylvia Hanika, a 6-2, 6-3 winner over Bonnie Gadusek, came through the quarterfinals unscathed.

Navratilova could do no wrong last night as she advanced to the semifinals, in which she will play Potter today at Capital Centre.

Both Shriver, from Lutherville, Md., and Smith started off shaky, losing serve the first time. But only Shriver remained discombobulated. Smith, who will play Hanika in the other semifinal today, said, "We both started out nervous. It's hard for Pam. Basically, it's her home town. She wants to play so well. That's not the best . . . she missed some balls she doesn't usually miss."

It was an interesting contrast of personal styles if not tennis styles. They both play the same game, serve and volley. Smith was just that much sharper, that much crisper, throughout. But where Smith is constrained, Shriver is demonstrative. She is the Marcel Marceau of the tennis court. You always know what she's feeling. "Yeah," she said, "I pretty much tell you."

And, from the very beginning, she wasn't feeling good. "I never felt comfortable," she said. Partly, it was nerves before a crowd filled with partisans.

"Last night, I walked into the stands to talk to a friend and half the row thought I was coming to talk (to them)."

Shriver's volleys were errant, her serves not as overwhelming as usual. Smith broke her at 2-2 in the second set, when Shriver hit a backhand volley wide, and again to go ahead 5-2 when she hit a forehand winner off Shriver's second serve. Smith had a set-point in the ninth game but Shriver, struggling as she did all match, managed to hold serve: 5-4.

Serving for the match, Smith suddenly became jittery, missing all four first serves, and double faulting twice, to make it 30-30. Then Shriver hit a backhand chip shot wide and it was match point.

Again, Smith missed her first serve. But next she did something strange and wonderful. She went for an ace on her second serve. It was down the middle. Shriver, as startled as was everone else, managed just to pop the ball up back over the net. Smith put away the point, the game and the match with an overhead that was beyond even the 6-foot Shriver. Then again, she had been in over her head all night.

The seventh-seeded Potter, the consummate Connecticut Yankee, momentarily abandoned her patrician manner when she had defeated Jaeger, thrust both fists into the air and danced off the court.

Potter beat Jaeger with very big serves, six of them aces, four of them consecutive, and equally overwhelming overheads. But Potter also won with something else, something that does not come as naturally.

"I've been working a lot lately on playing the important points tougher," she said. "Despite missing a few, I think I was a little tougher than Andrea on those today . . . I don't think I've ever played the big points against a big player as well as I did today."

She broke Jaeger's serve, to go up, 4-2, in the first set, with two drop shots, one hitting the net cord and bouncing over. She came off the court, giving the thumb's up sign. In the next game, Potter fell behind on her serve, 0-30, and came back to hold, with two overheads, a service winner and a backhand cross court winner off an approach shot. Serving for the set at 5-3, she again fell behind, 0-30, and came back to win the game and the set, polishing it off with two service winners.

In the second set, Potter was down, 1-2, and it was Jaeger's ad. Potter, the nasty lefty, came up with three aces--one deep in the corner to Jaeger's backhand, one down the middle, the third into the corner again--to win the game and tie the set, 2-2. She then broke Jaeger, when Jaeger double faulted at 30-40, to go up, 3-2, and victory seemed imminent.

But Jaeger, who is nothing if not relentless behind those big eyes and long pigtails, broke back, with a backhand, cross court passing shot, her first winner off a return. That evened the set at 4-4.

At one point in the tie breaker, which should favor the big server, Jaeger led, 3-1. But Potter won the next four points, two courtesy of unaccustomed unforced errors on Jaeger groundstrokes, another on the kind of forehand winner from the baseline that is usually Jaeger's forte.

The concentration wavered. With Jaeger serving at 5-3, Potter hit a sloppy forehand return on a second serve. Jaeger earned the next point, off Potter's serve, with a great get of a volley at her feet. Suddenly, the tie breaker was even.

Then Potter served a winner and was ahead, 6-5. On match point, the two women exchanged countless moonballs and topspin forehands, driving each other deeper and deeper behind the end lines. Finally, Potter got what she was looking for: a ball short enough to volley. She put it, and Jaeger, away with a cross court backhand.