One of the wildest first weeks in the history of the Wimbledon tennis championships came to a startling end today as john McEnroe, physically stiff and lacking his usual emotional fire, was beaten in straight sets, 6-4, 6-2, 6-4, by Tim Gullikson.

McEnroe, the gifted but volatile 20-year-old left-hander from Douglaston, N.Y., was seeded No.2 and heavily favored to reach the final next Saturday likely against defending champion Bjorn Borg or No.3 Jimmy Connors, who both won today and escaped the unprecedented upheaval of the first week.

But on a gray and gloomy Middle Saturday -- historically, a notorious upset day at the All England Lawn Tennis and Croquet Club -- a chilly breeze blew all for McEnroe

He had a cold. The strained muscle in his left thigh that has bothered him since mid-May was sore. He felt tight and sluggish, unable to react with anywhere near his usual quickness.

And he ran into Gullikson, the No.16 man in the computerized world rankings of the Association of Tennis Professionals, on a very good day,

Largely because Gullikson applied amost relentless pressure with a solid serve-and-volley attack and some clever tactical variations, nothing went right for McEnroe.

He served poorly. He returned serve inconsistently. He got caught surprisingly out of position on volleys he usually makes with the surest of touch.

And in the middle stages of the match -- until he fought back from 0.4 to 4.5 in the third set, and had two break points to level at 5.5 -- he started feeling sorry for himself, and played with totally uncharacteristic resignation.

McEnroe, who two years ago qualified for Wimbledon and then astonishingly became the youngest semifinalist in the history of tennis oldest tournament, came here with high hopes, and was expected to measure up to great expectations.

But since arriving in England three weeks ago, and promptly winning a grass-court tournament at queen's Club after four weeks off to recuperate from the groin pull he suffered in Tokyo, McEnroe has been under pressure.

Always a ferociously competitive and self-critical player with a dour on-court disposition, he was labeled "Superbrat" by the British press and harshly criticized for a couple of mildly petulant incidents at Queen's

No one doubted his ability to win Wimbledon -- after all, he has swiftly risen to the No.3 world rankings, and beat Connors and Borg back to back to win the World Championship Tennis finals at Dallas in May -- but the press here lectured him sternly on his demeanor.

This all seemed to weight on McEnroe. He lost his serve in the fifth game -- the only service break in the first set -- when a spectator stood up in the press box and verbally assailed him for questioning a "fault" call.

The offending spectator, who was not a reporter as McEnroe thought, was ejected by a steward, but McEnore lost the game and stewed inside.

He continued to fret throughout most of the match. He kept his temper but the customary internal combustion that seems to drive him was conspicuously missing. He flubbed shots and did not chastise himself. He was subdued, lifeless, almost expression-less until his brief third-set revival -- which was clearly too little and too late.

"He's not playing nearly as well as he was. He's not serving as well, and the whole match -- just looking across the net at him all the time -- he really seemed like he was unsettled. It just seemed like there were a lot of things on his mind," said Gullikson, 27, who played the match of his life to reach the quarterfinals of a major tournament for the first time.

"Maybe it's the tremendous pressure that's been put on him. He's been kind of labeled as a bad boy, which he really isn't. He's only 20 years old, and really everybody taught he was going to win Wimbledon this year. That's a lot of pressure on anybody, and you can't play well all the time. There are a lot of good players out there."

Boeg, who produced blistering service returns and passing shots when he needed them most to beat aggressive California Brian Teacher, 6-4, 5-7, 6-4, 7-5, will next play Tom Okker, whom he beat in the semifinals last year. Okker, 35, today beat Gene Mayer, 7-6, 5-7, 6-4, 6-4.

Connors, who routed Mark Cox, a 35-year-old British left-hander, 6-2, 6-2, 6-1, on Centre Court -- will play Bill Scanlon, who blew a 6-1 lead in losing the third-set tie breaker but came back to oust Brad Drewett, 6-4, 6-4, 6-7, 7-5.

In the bottom half of the draw Italian Adriano Panatta [a 7-6, 6-3, 7-6 victor over Sandy Mayer] plays Pat DuPre [who beat Bob Lutz, 3-6, 7-5, 4-6, 6-4, 7-6], and Tanner [who lost his first set of the tournament but beat Jose Clerc, 6-7, 7-6, 6-4, 6-1] plays Gullikson, who has beaten him in their only two previous meetings.

The women's single's also heated up after a comparatively calm first week, but the tip eight seeds reached the quarterfinals and produced these pairings for Monday: defending champion Martina Navratilova vs. Dianne Fromholtz, Tracy Austin vs. Billie Jean King, Virginia Wade vs. Evonne Goolagong and Christ Evert vs. Wendy Turnbull.

Navratilova, who was suffering from a cold and a pulled leg muscle, struggled against Greer Stevens, who kept her under pressure until taking a nasty fall in the sixth game of the third set.

Stevens, who wears a heavy brace to protect the right knee in which she needed a ligament transplant last year, limped badly thereafter, couldn't keep up her blazing assault, and Navratilova squeezed through, 7-6, 6-7, 6-3.

Two of the three Australian women in the quarters were taken to three sets -- No.3 Goolagong by improving 20-year-old Kathy Jordan, and Wendy Turnbull by fellow Australian Kerry Reid.

But all else that happened today paled in comparison to McEnroe's demise on claustrophobic Court No.2.

McEnroe had beaten Gullikson's left-handed twin, Tom, on the same court Friday, but came up stiff after playing doubles until 9 o'clock Friday evening.

"I knew I was in trouble right from the very begining. I felt really sore. I had a coule of break points early and I just wasn't moving to the ball. Even on my serve, I wasn't getting up on the ball, I was missing," said McEnroe

"Tim was playing really well, too. He bore down on me and kept on the pressure except for one game I broke him [at 1-4 in the third set]. He played a smart match, a good match. That's what it came down to." CAPTION: Picture, John McEnroe, left, congratulates victor Tim Gullikson. UP,