Taking up where they left off in the U.S. Open final four months ago, punishing each other with concussive pace and making every long rally into a war, Guillermo Vilas and Jimmy Connors went into a third set tonight in their match in the $400,000 Colgate Grand Prix Masters tournamenT.

Vilas, who beat Connors in fours sets at Forest Hills, got two early service breaks for a 4-1 lead and held on to win the first set, 6-4. Commors jumped out to a 3-0 lead in the second and served it out at 6-3 to even the best-of-three set match.

Wimbledon champion Bjorn Borg and Brian Gottfried, the "forgotten man," earned berths in Saturday's semifinals with torturous three-set victories in today's afternoon session.

Gottfried took slightly less than 2 1/2 hours to subdue Raul Ramirez, his doubles partner and longtime sigles rival, 6-7, 6-2, 6-4, on the medium-pace synthetic court.

Borg then weathered a stretch of superb lefthanded serves by Roscoe Tanner to win a 2-hour 2-minute struggle, 6-4, 7-6, 6-3.

Manuel Orantes stayed alive in the round-robin portion of the Masters, the final playoff for the top eight singles finishers and top four doubles teams in the 1977 Colgate Grand Prix point stanlings, by beating Eddie Dibbs, 7-6, 7-5, in the first match of the evening session.

Gottfried and Borg are assured of places in the semifinals because they have 2-0 records. The top tow players in each of two round-robin groups advance to the semifinals of the eightman playoffs.

In Wednesday's first-round matches, Gottfried beat Tanner, 7-5. 6-2, and Borg routed Ramirez 6-2, 6-4. The back-to-back losses have eliminated Tanner and Ramirez from contention for the $100,000 first prize.

Ornates, who lost to Villas, 6-4, 6-1, on opening night, is 1-1. Dibbs, a 7-5, 6-4 loser to Connor Wednesday, is 0-2 and out of the running.

The remaining two semifinalists will be decided Friday when Connors plays Orantes and Vilas faces Dibbs.

The marathon matinee session, which began at 2 p.m. and did not end until 6:53, nearly overlapped the 7 p.m. starting time for the night program. This caused ugly crowd scenes outside the Garden among evening ticketholders, who were made to wait in a jammed lobby or outside in the cold until afternoon customers vacated the arena.

A capacity crowd of 18,590 attended the evening session, drawn mainly by rematch of the epic Forest Hills final that Vilas won over Connors in fourth brutish sets, 2-6, 6-3, 7-6, 6-0.

The Borg-Tanner match, which gave an extra measure of afternoon delight to the matinee crowd of about 9,500, had a peculiar pattern. There were five service breaks in the first set, none in the second (which Tanner won in a tiebreaker, seven points to five by taking five of the last six points), and one in the third.

Eventually, Borg's extraordinary quickness and reflexes, combined with his deadly passing shots, overcame Tanner's heavy serving and volleying. Tanner served 13 aces, some of them downright electrifying, but he couldnt't get his quick and deceptive first delivery invwhen he needed it most.

That was in the fourth game of the final set, in which Tanner led, 40-15, then lost his serve after five deuces and four consecutive Borg advantages.

The last two points of this critical game typified the match.

Tanner floated a backhand long after one of the long rallies in which he could not hope to keep up with Borg's steadier, heavily topspun groundstrokes.

That gave Borg his fourth break point. On it, tanner did get to the net, but he had to stretch for a volley that had little penetration on it. Borg cranked up and whacked a backhand cross-court passing shot.

Disheartened, Tanner butchered two backhands and an overhead to fall behind, 15-40, in his next service game, but Borg couldn't delever the knockout. Still, the 21-year-old Swede had no trouble there after, holding his serve at love with his fourth ace for 5-2 and at 15 for the match.

Gottfried was 10-9, lifetime, against his doubles partner coming into today, but Ramirez held a 3-2 edge in 1977.

Gottfried had an early break in the final set today, lost it, then hung on by the tips of his fingernails. He won five straight points from 0-40 in the sixth game and survived two more break points in the eighth game, which went to deuce four times.

Gottfried got the decisive break in the next game, hitting two fine passing shots - a backhand cross-court and a forehand cross-court - from 15-30. Then Ramirez, perhaps putting extra pressure on himself because he knew he had let so many chances slip away, double-faulted for the break to 4-5. Gottfried served out the match.

Dibbs - who served for the first set against Connors Wednesday but fell apart after blowing an easy overhead at 5-4, 15-0 - found himself in a similar situation tonight.

He led Orantes, 5-3, but double-faulted on the first point as he served for the set and was broken at 12.

Oranites ran off 12 straight points - holding at love for 5-5, breaking at love for 6-5, and getting to 30-0 as he served for the set - but then faltered and lost his serve to send the bizarre set into a tie breaker.

Orantes, an artful lefthander who won the masters at Houston last year over a field that lacked Borg and Connors, ran through the tie breaker, 7 points to 2. He ran promptly played an atrocious game, lost his serve at love, but broke right back to 1-1 in the second set.