It was somehow fitting that a typically bustling, frenetic middle Saturday at Wimbledon should be crowned with a historical milestone. Bjorn Borg won his 31st consecutive singles match in the world's premier tennis tournament today, tying the record held by Australian Rod Laver. But it wasn't easy.

Like several other favorites, including defending women's champion Martina Navratilova, Borg was forced to show his championship meddle on a cold, blustery, occasionally drizzly day at the All England Lawn Tennis and Croquet Club.

Playing late in the day, as chilly overcast edged toward darkness, Borg needed nearly three hours to defeat a tenacious, hard-hitting and psyched-up Australian named Rod Frawley, 6-4, 6-7, 6-1, 7-5.

Every set but the third was a struggle. Rawley, a burly and determined 28-year-old who knew he had nothing to lose and instant celebrity to gain, served well, rushed the net and hammered authoritative volleys. Frawley also whacked enough blistering returns of serve to make Borg wary. In short, he was just the type of bloke the four-time champion does not relish playing on fast, damp grass.

Twice in the fourth set, at 1-2 and 2-3, Borg had to fight off two break points. When he served for the match the first time at 5-4, Frawley broke him with a couple of blazing returns. When Borg finally finished his day's work, breaking Frawley for 6-5 in a memorably combative game and serving out the match at love, it was 8:15 on an evening that had a Siberian bite. The lights on the electric scoreboard of court No. 1 glowed like a neon sign in the gathering dusk, and Borg was less concerned with celebrating his landmark than going straight to the rubbing table for a massage.

Later, after a shower and a rub, he did talk about equaling Laver's consecutive victory streak at Wimbledon, set in 1961-62-68-69-70. (Laver did not play Wimbledon in 1963-67, when professionals were barred, but won four times in a row in the years that he played. Roger Taylor finally beat him in the fourth round on a similarly bleak and windblown middle Saturday in 1970).

"I feel very, very satisfied," said Borg. "It's not too easy to win 31 straight matches here, and I finally did it." Borg will attempt to break the record in his fourth-round match against Hungarian Balazs Taroczy and to become the first man since Lawrie Doherty in 1902-06 to win the singles title five successive years.

"I never thought about it during the match, I didn't have it in my mind, but for sure before the match, I knew if I won I would equal the record."

Borg's triumph was only one of many noteworthy events on a day that throbbed with activity, excitement and drama from just after mid-day (rain delayed the start of John McEnroe's 6-0, 7-6, 6-1 victory over Tom Okker on Centre court by 15 minutes) to nightfall, when Gene Mayer eliminated Adriano Panatta, 6-3, 6-3, 6-2, in marginally playable light.

Several of the top women's seeds -- No. 1 Navratilova, No. 2 Tracy Austin, No. 3 Evonne Goolagong Cawley and No. 7 Virginia Wade -- suffered some anxious moments in three-set victories.

Five of the lesser men's seeds -- No. 8 Victor Pecci, No. 9 Pat DuPre, No. 10 Ivan Lendl, No. 15 Stan Smith and No. 16 Jose-Luis Clerc -- were beaten by industrious serve-and-volley players, some of whom have been around Wimbledon a long time and have interesting tales to tell.

Other seeded men were pushed to four tough sets -- No. 3 Jimmy Connors by Heinz Gunthardt of Switzerland, who played a dream of a first set and won it in a tie breaker, 7 points to 1; No. 4 Vitas Gerulaitis by Californian Bruce Manson, and No. 7 Peter Fleming by the mercurial Ilie Nastase, who could have won if he had played as well in third and fourth set tie breakers as he did the rest of the match.

"Wind, rain, waiting around, wet and chopped-up grass, matches that are interrupted two or three times, that's what this tournament's all about," said Don Candy, coach of Pam Shriver of Lutherville, Md., who today beat Barbara Jordan, 6-4, 6-4, to advance to a fourth-round meeting with Billie Jean King. "Tennis aside, you have to be a special kind of person to win here. You have to be a tough nut -- a tough, tough nut."

Navratilova was. She was down a break at 1-2 in the final set against Tanya Harford, a bouncy, 22-year-old South African who battles for every point like a hungry bulldog.

Harford, who took a set from Navratilova in her opening match last year, had a good spin serve and short-angled volleys that worked well on the soft and uneven grass of court No. 2, "a court that can be a great equalizer," said 1978-1979 champ Navratilova, who historically has had difficulties on outside courts and middle Saturdays here.

The match was twice delayed by rain. Harford, ranked No. 41 in the world, was going for every shot, diving around the court fearlessly, sliding tricky returns that taxed Navratilova's volley.

Navratilova was moving so stiffly that her father sent a message, delivered by her mother along with a couple of kisses during the first rain delay. To bend her knees more.

But she came through with the big shots when she needed them -- a running forehand cross-court pass from far behind the court immediately followed by a forehand down-the-line return that broke Harford's serve in the eighth game of the final set. Thus inspired, Navratilova served out at love for a 6-3, 3-6, 6-3 triumph.

Next door on court 3, which was in even worse shape, Austin was having all kinds of difficulty returning the snake-like left-handed services of Barbara Potter, 18, an aggressive player from Waterbury, Conn., who eventually helped undo her own good efforts by double-faulting four times on break points, twice in the final set.

"It was tough to break serve, because I always felt like I was returning from a mud puddle. It was tough to move out there, and she was playing very well," said Austin, who dropped a tie breaker, 7 points to 3, but won comfortably in the third, 6-2, 6-7, 6-2. goolagong lost the first set to 6-foot veteran Betty Stove, the 1977 runner-up to Wade, on Centre Court, but was never in trouble again after breaking for a 2-1 lead in the second set. Stove contributed with a double-fault and a bungled backhand volley before Goolagong broke with a forehand passing shot and glided away to a 3-6, 6-2, 6-3 triumph.

Wade, still the Last British Hope at age 35, had a more trying match against Betsy Nagelsen. She trailed the 23-year-old Floridian -- aptly characterized by the BBC radio commentator as "A very fine player, but not a winner" -- by a set and 3-1 before squeaking out a 6-7, 7-5, 6-3 victory.

Nagelsen had a break point at 4-4 in the second set, and three full swings at the ball in a scrambling point, but she didn't go for it. Instead she lobbed, chipped a backhand, then lobbed wide -- a tentativeness on the critical points that is the root of her problems.

The quality of this match on windswept court 1 was not very high until after Wade led, 5-0 in the final set. Then Nagelsen started drilling her returns, saved eight match points (four on Wade's serve, four on her own), broke back to 2-5 and nearly to 4-5 before losing, 6-7, 7-5, 6-3.

The No. 3 seed, Chris Evert Lloyd, walloped Lindsay Morse, 6-1, 6-4; No. 5 Billie Jean King roasted Peanut Louie, 6-2, 6-2, and 15-year-old newcomer Andrea Jealger spanked Jane Stratton, 6-1, 6-1, setting up the most attractive women's fourth round here in many years.

The pairings in draw order, top to bottom: Navratilova vs. Kathy Jordan, King vs. Shriver, Evert vs. Joanne Russell, Wade vs. Jaeger, Wendy Turnbull vs. Lele Forood, Cawley vs. Hana Mandlikova, Dianne Fromholtz vs. Greer Stevens and Austin vs. Terry Holladay.

The men's pairings, heading into the second week after the traditional Sunday off, are: Borg vs. Taroczy, Mayer vs. Colin Dibley, Gerulaitis vs. Wojtek Fibak, Brian Gottfried vs. Phil Dent, Roscoe Tanner vs. Nick Saviano, Connors vs. Hank Pfister, Fleming vs. Onny Parun, and McEnroe vs. Kevin Curren.

Californians Saviano and Pfister prevailed in the day's only five-set matches.

Saviano, a left-hander who now lives in Florida, followed up Friday's marathon victory over Englishman Buster Mottram (13-11 in the fifth set) by outlasting DuPre, last year's surprise semifinalist, 7-6, 1-6, 7-5, 11-9. Pfister, an explosive serve-volleyer, beat 1979 quarterfinalist Tim Gullikson, 4-6, 6-3, 7-5, 1-6, 6-2.

Pecci and Lendl, richly talented young players who are more comfortable on slower courts that give more predictable bounces, were beaten by veteran Australians Dent and Dibley, each in four sets.

Perhaps the best human interest story of this Wilbledon is the comeback of Parun, a 33-year-old journeyman recently returned to the circuit for a final fling after four serious neck operations.

A former Wimmbledon quarterfinalist this straightforward and eminently likable New Zealander was ranked No. 185 in the world three weeks ago, when he decided to try a new racket with an oversized head. Since, he has won a grass court tournament at Beckenham, played through the rugged Wimbledon qualifying and won three matches in the main draw.

More interesting, he wears a string that hangs from his shirt while he plays, reminding him not to snap his neck too far when he serves -- a contributing factor to the ailment that necessitated surgery.