Men's quarterfinal day at Wimbledon began this afternoon predictably enough, at 2 p.m. precisely with Bojorn Borg breaking Tom Okker's serve in the first game and dooming "The Flying Dutchman" to a 67-minute voyage to ignominious defeat, 6-2, 6-1, 6-3, on Court No. 1 at the All England Lawn Tennis and Croquet Club.

The day ended 5 hours and 52 minutes later with a much-less-likely scene as the sun dipped beneath the walls of Centre Court -- the several hundred vocal Italians who had serenaded Rome's favorite son, Adriano Panatta, from the standing-room sections, mournfully silent as their hero fell to astonishing Pat DuPre, 3-6, 6-4, victory over 22-year-old Bill Scanlon, who led, 5-2, in the third set before suffering a classic case of cement in the elbow.

Roscoe Tanner, serving and volleying with concussive efficiency except in the tie breaker that decided the third set, hammered Tim Gullikson, who had beaten John McEnroe in straight sets Saturday, 6-1, 6-4, 6-7, 6-2. In short, just another wild afternoon in Wimbledon's wacky 102nd year, which bounces back to the women Wednesday for their singles semifinals: defending champion Martina Navratilova vs. Tracey Austin, and 1974-76 champion Chris Evert vs. 1971 queen Evonne Goolagong.

They are the top four seeds, and any one of them should have a reasonable chance of winning it all.

Not so with the men. Logic suggests that their singles title will be decided realistically, if not officially, in the semifinals Thursday when Borg, who is seeking his fourth consecutive title, plays Connors, the champion in 1974 and runner-up three of the past four years.

They have been the finalists here the past two years, Borg winning a 3 1/2-hour match in 1977 -- 3-6, 6-1, 6-2, 5-7, 6-4, -- and a startlingly brisk romp -- 6-2, 6-2, 6-3 -- last year.

Connors got revenge over a blister-thumb Borg, 6-4, 6-2, in the final of the U.S. Open last September. "Right after that match, I forgot it because I wasn't able to play my best," said Borg, who is too good a player to need physical copouts for his defeats, but nevertheless, always has them at the ready.

But Borg has won their two meetings this year decisively -- losing only 10 games in four sets against Connors in the finals of tournaments at Boca Raton, Fla., and Las Vegas, and was in much better form today.

The 23-year-old Swede returned the serve savagely and ripped blistering passing shots off both wings against the light-hitting and resigned Okker, 35, whom he had thrashed with similar ease in last year's semifinals.

Borg served and volleyed splendidly, too, begrudging Okker only 16 points in a 21-minute first set, 14 points in a 21-minute second set, and 24 points in a 25-minute third set.

Connors, by contrast served fitfully, reacted with nowhere nar his usual quickness on returns of serve, and struggle to find the timing on his approach and passing shots, both off his normally reliable backhand and normally suspect forehand.

In fact, he might have found himself in an uncomfortable fifth set, or even wose, if Scanlon -- the once-promising NCAA champion of 1976 who last year lost in the first round of 23 consecutive tournaments before getting into a Grand Prix tournament in Hawaii as qualifying "lucky loser" and winning it -- had not choked badly at 5-3 in the third.

Solid and occasionally brilliant up to then, which is more than could be said for Connors, Scanlon pushed two forehand volleys long, double-faulted once,, then netted a backhand volley as he served for the set. He was similarly dreadful in losing the tie-breaker, 7 points to 1, and in fact won only seven points from the times he took a 5-2 lead in this pivotal set.

Bog has been so swift and sharp in his last three matches -- ever since his coach, Lennart Bergelin, said he might quit with a phantom pulled thigh muscle -- that logic dictates he will whip Connors for the eight time in their last 11 meetings, and go on to win his fourth straight title, which no man has achieved here since New Zealander Tony Wilding in 1910-13.

But what place has logic in a Wimbledon that has produced as a semifinalist Patrick Marie DuPre, who said after bumping off No. 4 seed and two-time semifinalist Vitas Gerulaitis on opening day: "I consider myself basically a pretty horrendous grass-court player."

"Well, I seem to be picking up the game a little better. Obviously, I must be doing something right," DuPre said after his marvelously gutsy 3 hour 28 minute victory.

"Every match I play is icing on the cake for me. I'm really just going to fight like mad, to try and go as far as I can. If I win on Thursday [against third-time semifinalist Tanner] I don't see any reason why I can't win on Saturday, too."

"I just feel like no matter what's going to happen. I'm going to win. I felt that way today, and in every other match -- that I can win and have the game to win."

DuPre -- No. 28 in the U.S. rankings and No 37 in the computerized world ranking, but so little known that even the exacting Wimbledon program continues to list his name incorrectly, without the "p" capitalized -- is almost as unlikely a semifinalist as the 18-year-old McEnroe was as a qualifier two years ago.

"Before I beat Vitas, I had never really won a match of any consequencve on grass," said the 1976 Stanford graduate in economics, a 24-year-old son of Belgian parents who emigrated to Birmingham Ala., when he was 2 years old.

His father, manager of a steel plant in the Birmingham suburb of Anniston, and mother have been calling him every night recently, arranging interviews with the Alabama media for the new local celebrity. He has also been swamped with trans-Atlantic calls from newspapers and radio and television stations in his adopted hometown of San Diego.

DuPre played for the first time today on Winbledon's legendary Centre Court -- which can be intimidating enough even without the presence of all those Italians, applauding rhythmically and chanting "A-dri-a-no." [clap-clap-clap] for the dashing Panatta, the noblest tennis-playing Roman of them all.

DuPre started shakily, losing his serve in a long first game [three deuces] on his fourth double fault. He served two more of his total 14 double-faults in the next game, and seemed destined for a quick exit as he fell behind, 3-6, 0-4.

"The nosiy Italians didn't bother me, because I expected that all along. I think the reason I didn't play well at the beginning was that I was a bit nervous about playing in the Centre Court, which everbody agrees is the greatest court in the world, and it took a while to get used to the perspctive," said DuPre.

"It's so much bigger than the other courts, and the backstops are so much farther behind the court, that it takes some time for you to adjust and start timing the ball. But being on that court was just great . . . it's a little quicker and bounces much truee than the other courts. . . I just loved being out there."

Panatta had never before been beyond the third round at Wimbledon, but his elegantly powerful game -- big serve, decisive and sometimes diving ved with touch -- is volleys, pace tempred with touch -- is ideally suited to grass courts.

Only his concentration, his mental toughness is suspect -- this despite his winning the Italian and French Opens on clay in 1976 -- and today the suspicious were justified.

"After I led by one set and 4-0, I should have tried harder instead of thinking I already had the second set. I had two breaks, I thought it was over, and I just relaxed a little bit. Then DuPre came back very good and played very solid," said the sloe-eyed Panatta afterward, explaining the run of seven consecutive games that took DuPre to 1-0, in the third set.

Panatta led, 4-2, in the third set, lost the break, but seemed to have the match back in hand when he won a tie breaker, 7 points to 3, with two of his 12 aces and a blazing backhand cross-court return winner of a fine first serve on the pivotal fifth point.

But DuPre kept serving and volleying purposefully, whacking his returns, and getting enough passing shots past Panatta's lunging volleys to scrape back in.

One service break, as Panatta bungled a backhand volley at 2-2, 15-40, decided the fourth set. Then Panatta lost his serve on double-fauts in the first and third games of the fifth. CAPTION: Picture, Pat DuPre displays the form that has given him a place among the final four at Wombledon. He defeated Adrino Panatta in the quarterfinals, 3-6, 6-4, 6-7, 6-4, 6-3. UPI