The trend of the "Wednesday Night Massacre," when Bjorn Borg, Ilie Nastase and Manuel Orantes were all upset, continued today as Adriano Panatta, Harold Solomon and Eddie Dibbs were eliminated from the U.S Pro Indoor tennis championships in thirdround matches at the Spectrum.

At the end of the 24 hours of upheaval, No. 1 Jimmy Connors, the defending champ, was the only one of the top eight seeds left in the strong $200,00 tournament, the biggest of the 12 events in the "World Series of Tennis" (formerly the "World Championship of Tennis") that leads to the rich WCT playoffs in May.

As favorites became an endangered species, Tony Roche, Jeff Borowiak, Bernie Mitton, Vijay Amritraj, Cliff Drysdale and Dick Stockton moved into the quarterfinals - an unlikely crew for such an important tournament, and solid evidence that all the talk about the depth of talent in men's tennis today is more than mere hoopla.

"It's like the old cliche about pro football, that on any given day anybody can beat anybody else," said Solomon, the Silver Spring, Md., native who was seeded No. 6, behind Connors, Borg, Nastase, Orantes and Panatta.

"There are just a lot of awfully good players around today," added Solomon, a 6-0, 6-4 loser to Borowiak. "If you let down just a little bit, you're in big trouble."

Borowiak, a richly talented but inconsistent 27-year-old Californian who jumped on Solomon at the start and never let him into the match, was asked afterward whom he would like to play for the $40,000 top prize if he gets to the final here.

"Nancy Richey," was his deadpan reply.

Considering the absurd things that have been happening, that was a perfect answer. It started Wednesday night when, in rapid succession, Nastase was beaten for the second time in three weeks by 20-year-old NCAA champ Bill Scanlon: Orantes was cut down by Fred McNair of Chevy Chase, Md., and Borg was ousted by Ray Moore.

Two of Wednesday's assassins became Thursday afternoon victims: Scanlon, who reached the final of his first WCT tournament after beating Nastase in Birmingham, Ala., fell to 35-year-old Cliff Drysdale, 6-3, 7-6, and McNair, still weary from what he called "the bigget singles victory of my career," was dispatched by Amritraj, 6-2, 5-7, 6-3.

Roche, the 31-year-old Australian lefthander who was runner-up to Rod Laver here in 1969 and 1970, hit some wonderful angled volleys and chipped returns to defeat Panatti, the Italian and French Open champ, 6-3, 6-4.

Mitton - who could be Central Casting's idea of a pirate with his black beard, gold front tooth and flashy, washbuckling style - hit some spectacular winners in forcing seventh-seeded Eddie Dibbs to walk the plank, 6-4, 4-6, 6-3.

Stockton, the No. 12 seed who had to go to 7-6 in the third set to beat John Alexander on Wednesday, served and volleyed strongly to uproot the No. 8 seed, Brian Gottfried, 6-3, 6-2.

Borowiak, the 1970 NCAA champion from UCLA, is 6-foot-4, with enormous reach at the net and a crunching, unerring overhead. He is a streaky player, and today he started in high gear and simply ran over the 5-6, 138-pound Solomon, who got so frustrated he batted two balls into the upper deck of the cavernous arena.

"I didn't think Harold was off that much. I just felt that I could hit every ball with pace where I wanted to," said Borowiak, a native of Berkeley who is one of the free spirits of the pro tour.

"I've been practicing a lot, doing a lot of conditioning, running, drills, mixing it all up," said Borowiak, a bright young man who is as much at home discussing comtemporary music and literature as tennis. "I'm pretty confident now. I won an eight-man. $20,000 tournament in Seattle a few weeks ago, beating four pretty good players - (Charlie) Pasarell, (Marty) Riessen, (Rod) Laver and (Tom) Gorman."

Borowiak was surprised at how well Solomon returned his high-velocity first serves ("he seems to see them in slow motion"), but it was the lanky Californian who hit the majority of winners in the match, especially some lovely backhands.