The Wimbledon tennis championships enter their climactic second week Monday with Bjorn Borg still a solid favorite to win his fifth consecutive singles title, the top seven men and top 11 women still alive, and the tournament still a day behind schedule because of first-week rains that have left the grass courts of the All England Lawn Tennis and Croquet Club soft, spongy, and full of curious bounces.

Ordinarily, the singles events are at the quarterfinal stage at the end of the first week, and the tournament takes on an entirely different character. It becomes more a series of carefully staged duels (the first at 2 p.m. precisely, the second to follow straight away) than an all-day free-for-all and crap shoot.

Traditionally, the men and women play singles on alternate days the second week -- the ladies on Monday, Wednesday and Friday, the gentlemen on Tuesday, Thursday and Saturday. All matches are played on the coddled turf of Centre or No. 1 courts -- the adjacent, enclosed arenas that accommodate 7,000 and 15,000 spectators, respectively. The players have a day of rest between their matches.

But this has not been an ordinary year at Wimbledon. Persistent rain and wind -- and even hail -- have prevented the players from reaching their appointed rounds on schedule. Three rounds of singles have been played, instead of four; at least two more of the long, congested, frenetic days so characteristic of Wimbledon's first week remain.

Weather permitting, all the men's and women's round-of-16 matches will be played Monday, and all the quarterfinals on Tuesday. Thus, important singles matches will be played "out in the country," as the outside courts are known.

Bad grass can turn a close match into a lottery, and those favorites relegated to the outside courts will be at somewhat of a disadvantage.

Billie Jean King will play Pam Shriver of Lutherville, Md. -- who was born the year Billie Jean played her third Wimbledon -- on Court No. 2, whose soft and chopped-up grass often has been a favorites' burial ground. Brian Gottfried will face Australian Phil Dent on the same court. g

Chris Evert Lloyd, who has never failed to reach the semifinals in eight previous Wimbledons, will play fellow Floridian JoAnne Russell next door on Court no. 3, which is even muddier and more unpredictable than No. 2 this year. Roscoe Tanner and Nick Saviano, left-handers whose snake-like serves can produce more wild bounces than a crooked roulette wheel, will follow there.

Colin Dibley, 35, an Australian who served his way into the Wimbledon quarterfinals in 1971 and 1972, will play Gene Mayer -- the No. 6 seed, and perhaps the most underrated player in the world -- on Court 4.

Peter Fleming and Onny Parun, a 33-year-old New Zealander who fought his way through the qualifying tournament to make a sentimental last fling at Wimbledon following four neck operations, will direct heavy serves and volleys at one another on the skiddy grass of Court 5.

Dianne Fromholtz and Greer Stevens, seeded eighth and 11th in the women's singles, will play on Court 13, out by the vinecovered water tower, the groundmen's nursery and the corporate entertainment marquees that have added a new look to the Wimbledon skyline in recent years of increasing, but tasteful, commercialization.

Play is scheduled to commence at noon, two hours earlier than usual, but the ambitious schedule on Centre and No. 1 courts assures that some players will be battling at nightfall. Strange things can happen at Wimbledon in the long shadows of evening, when the courts are slick, the air is chilly and the underdogs are wont to go for the throat.

Monday's schedule on Centre Court is a rich one: 1971 champion Evonne Goolagong Cawley against Hana Mandikova, the best young woman player in Europe; Virginia Wade, 35, versus Andrea Jaeger, 15; Vitas Gerulaitis versus Wojtek Fibak, a rivalry of undisguised bad blood, and then Borg, seeking the 32nd consecutive singles victory that would establish a Wimbledon record, against Balazs Tarcozy of Hungary.

The first two matches are especially promising. Goolagong, at 28 still the most lithe and graceful figure in the women's game, never has played Mandlikova, 18, a talented Czech whose aggressive game is well suited to grass. Goolagong says she is looking forward to it.

Wade -- "Our Ginny," to the British, an institution almost as venerable as Big Ben -- also is anxiously awaiting her first encounter with Jaeger, a delightful prodigy who shows no sign of being intimidated by anything or anybody.

"She plays a very good game and is good stuff," says Wade. "Of all the young players, she is the one I look forward to seeing. She is very confident without being cocky. She has a nice personality and is spunky."

She also could beat "Our Ginny" to a pulp.

The matches on Court No. 1 do not figure to be quite as absorbing, but there could be some little treasures there. Martina Navratilova, the 1978-79 champion, plays quick and aggressive Kathy Jordan, followed by Tracy Austin against Terry Holladay, John McEnroe against qualifier Kevin Curren, and Jimmy Connors against hammering Honk Pfisr.

In the early hours of the afternoon, Wimbledon will be a smorgasboard of tennis, spread out for sampling on far-flung, rectangular trays of white-liner grass. Later in the day, when the shuffling crowd starts to leave the outside courts and the shrill voices of hawkers peddling the afternoon's tabloids filter through the picturesque grounds, the focus of attention will move inside, to a drama that could well occupy the show courts until the edge of night.

It was like that Saturday. No matter where you looked, or when, it seemed as if interesting or poignant things were happening.

Several of the favored women teetered, but none fell, early in the day. Navratilova, Austin, Goolagong and Wade all lost sets. Navratilova and Wade were each down a set at the break. The last of the men's "clay court seeds" all were beaten: Victor Pecci by Dent, Jose Luis Clerc by the gutsy Parun, and Ivan Lendl -- who broke the string in his favorite racquet at match point down in the fourth set tiebreaker -- by Dibley, the former airport customs inspector who this day had something to declare.

Ilie Nastase, whose squabbles with local reporters prying into the recent breakup of his marriage were all over the front page of the tabloids again, lost a spotty but sometimes superb match to Fleming, decided by two tie-breakers.

McEnroe, serving and returning serves much better than in his five-set ordeal against Terry Rocavert the previous day, smoked Tom Okker in the first and third set, but was lucky to win the second and keep control after Okker had three set points in a tiebreaker.

Gottfried made Stan Smith, the champion of 1972, look sadly inept. Smith still is a proud and upright man, at 33 the last all-American boy of tennis, but he hardly could get a first serve in court, and was slow afoot, caught time and again volleying from awkward positions. It was not pleasant to see Smith go out so ingloriously.

On Centre Court, Heinz Gunthardt -- a talented 21-year-old from Zurich -- hit some great first serves and electrifying passing shots to win a splendid first set from Connors. He led 2-1, 40-0 in the fourth set, too, but Connors returned serve ferociously when he had to, showing glimpses of his old world-beating form in a match that considerably brightened the gloomy afternoon.

There was drama aplenty, but in the end, class generally prevailed. The favorites for the title pulled through and finally, at twilight time, there was Borg -- who has not lost at Wimbledon since Arthur Ashe beat him in the quarterfinals on July 1, 1972 -- surviving his annual first-week nervewracker against Rod Frawley to tie Rod Laver's all-time record of 31 consecutive Wimbledon singles victories.

"Playing late, it might be a little more gambling," Borg said. "You know, it gets dark, and windy, and you don't have the same feel, you don't see the ball as well as in daylight. He was playing very well, getting a lot of first serves in and not missing any volleys, so I was a little bit scared in this match."

Frawley, ranked No. 55 in the world, is an Australian who is back on the international circuit after taking four years off to teach tennis in Germany, where he still lives.

He was highly motivated for this match. "i never played Borg, and I was looking forward to it. In the second round I was down two sets to love (against Tony Graham, whom he beat, 13-11, in the fifth set), and getting to play Borg was the motivation for me. It wasn't a matter of getting to the third round at Wimbledon so much as wanting to play Borg," said Frawley.

"I've been playing very well since January, and I was psyched up for this match. I wanted to do well. It would be great to meet Borg at Wimbledon, you know, and in the back of my mind I knew if I played well, I might get picked for the Davis Cup Team. That's still very important for an Australian."

Frawley was well aware that the match was being televised live back to Australia even though it was early in the morning there.

It is precisely the risk of facing solid, workmanlike players with attitudes such as Frawley's on the erratic grass that makes the early rounds of Wimbledon such exquisite forture for players with lofty reputations they want to protect as much as to enlarge.

"The first week is definitely the toughest. That's when the guys who are supposed to do well really feel the butterfiles, because guys who have nothing to lose come gunning for them," says the now retired Arthur Ashe, the champion of 1975 who never got through the first week at Wimbledon thereafter. c

Little and middle-sized fish know that this is their sport's grandest and most closely watched pond, and if they can sneak up on a big fish here, the result causes a memorable splash. The ripples go around the world via television, radio, and newspaper headlines.

"Wimbledon only comes once a year. You wait 50 weeks for it," says Ashe. "Then if you lose in the first week on an outside court, that kills you more than if you lost a five-set match in the final. The pressure of the first week is brutal. If you make it past Saturday, at least you can relax."

Most years, but not this one. Monday will be, in effect, an extension of the first week, in all its delicious uncertainty.Last year, 11 of the 16 men's seeds lost on the first five days. This year has been much more in form so far, but many upsets could be due. Wimbledon is known for wild days when favorites fall in clusters.

"Normally it's nice to get through the first week," said McEnroe, the No. 2 seed and after his victory Saturday, best bet to beat Borg if he can reach the final. "But I was in the round of 16 last year (losing to Tim Gullikson on the middle Saturday), so I am only where I was a year ago. I don't regard it as having done better yet, though I want to keep on pushing."

McEnroe, who is sometimes too blunt for his own good, has complained about the pockmarked outside courts, the sometimes peculiar scheduling and the interminable waits for weather that make Wimbledon the most nerve-frazzling of tournaments.

"When you think about it, the conditions are terrible. There are a lot of things that aren't good about Wimbledon, but I guess as long as people say that this is one of the biggest tournaments, it's going to be," said McEnroe.

"Wimbledon and the U.S. Open are always going to be the biggest, I guess, because the players, the press and the public regard them that way. Some of the things that are done here are wrong. Who wants to play on wet courts? Sometimes you play late a couple of nights in a row, and then you are scheduled first match the next day. Things like that. But you've just got to cope with all that."

No one ever said that the world's premier championship should be easy to win. Only the fittest and best-prepared players do well here, those able to contend with the crowds, the noise, the claustrophobia and the nervous tension that comes from trying to maintain a fine competitive edge for hours while waiting to get on the court.

McEnroe understands. "I think the sign of a champion is to win when your're not playing well," he said. "Borg has won this title four times in a row, and he's been in some really tight situations where he wasn't playing his best tennis, but he's come out of them. You've just got to hang in there and find a way to win."

"Maybe it's the players who make Wimbledon such a big deal, or the fact that it's been going on so long -- the tradition," said Austin, the reigning U.S. Open women's champion at age 17. "At least for me, whenever I dreamed of winning one tournament, it was always Wimbledon. I still think it's the biggest title."