Dick Stockton, a colorless but ambitious and determined young professional, reached the final of the $200,000 U.S. Pro Indoor tennis championships today by beating an old personal nemesis, Jeff Borowiak, 6-3, 6-4, 7-6.

Stockton, seeded No. 12 in a tournament that vibrated with upsets earlier in the week (seven of the top eight favorites vanished before the quarterfinals), exerted relentless pressure on his own serve and complemented his agressive attack with resourceful bits of finesse.

The Philadelphia tournament, which traditionally draws the strongest field of the indoor season, is the biggest of the 12 "World Series of Tennis" tournaments that lead to the rich and prestigious World Championship Tennis playoffs inMay.

Stockton's opponent for the $40,000 top prize (Sunday WRC-TV-4) will be the winner of tonight's late semifinal between Jimmy Connors, the defending champion and No. 1 seed, and 35-year-old Cliff Drysdale.

Connors returning serve with a ferocity that knocked great cracks in the usually solid volleying of Tony Roche, ravaged the 31year-old Ausferocity that knocked great cracks in quarterfinals Friday night. Drysdale, also superb off the ground, beat Bernie Mitton, 2-6, 7-5, 6-3.

Roche again had trouble with his volleys, and was the vulnerable man on the court, as he and fellow Aussie Ross Case were victimized in the doubles semifinals by Wojtek Fibak and Tom Okker, 6-4, 7-5.

Stockton vs. Borowiak had some outstanding points, but until the end of the third set - when Borowiak finally broke Stockton as he served for the match at 5-4 and again at 6-5 - it never stirred the chilly crowd of 8,126 at the Spectrum, where the thermostat was turned down to conserve fuel during the current shortage.

Not surprisngly, Stockton didn't perceive the overall flatness of the contest, which at times was as dull as W. C. Fields might have expected a Saturday matinee in Philadelphia to be.

"I thought it was a good match, a tough match all the way through," said the 25-year-old native of Long Island, who was a four-time all-America in tennis and the 1972 NCAA singles champion for Trinity (Tex.) University. He now lives in Carrollton, Tex., outside Dallas.

Why did the crowd seem so apathetic until Borowiak broke back for 5-5 in the third with a spectucular game, and made his late flurry?

"I don't know," Stockton replied. "Maybe they were cold."

Borowiak - who has always troubled Stockton, and beat him in the final at Charlotte, N.C., in 1974 for his only WCT tournament victory - got closer to the heart of the matter.

"I felt I lacked a certain alertness from the word 'Go.' It sort of came to me in bits and pieces, but I felt I wasn't watching the ball intently throughout the match," said the 27-year-old Berkeley native; who captured the NCAA singles title for UCLA in 1970, the year before Connors arrived on campus and won it as a freshman.

Stockton, a dour competitor whose only changes of expression are from stern concentration to an occasional grimace of self-deprecation, determined the tempo of the match almost totally.

"Dickie is one of the best servers in tennis, as far as accuracy into the corners and depth go. He dictated the play most of the time on his serve," said Borowiak, an accomplished musician (piano and flute) who today could never find the melody he was searching for.

"He put pressure on all the time - serve and get in, serve and get in - and he executed that style very well. I'd say he controlled the pace, the tone, everything.

"I felt a little uncomfortable because my shots weren't flowing. I'm sure that was obvious," added Borowiak, rekindling thoughts of how many times he re-enacted a shot forlornly after missing it, as if wondering what was keeping him from executing it the way he has so many times in practice.

Borowiak, who only had one good chance to get into the match but let Stockton off the hook after having him 0-40 in the sixth game of the second set, played more from the backcourt than expected. Normally the quick, lanky, 6-foot-4 Californian is most intimidating from the net, where he can make the greatest use of his agility and reach.

"Jeff was playing well all week. I watched a couple of his matches and he's been content to stay back and rally and work his way into the net," observed Stockton.

Stockton got more than 75 per cent of his first serves in (75 of 99), and also got good depth and pace on his second serves. Browiak was not as accurate (53 of 86 first serves), and volnerable.

The importance of the second serve in this match was demonstrated early as Stockton broke for 3-1 in the first set, attacking four second balls, and then held for 4-1, winning four points after missing first serves.