At the beginning of the week, to celebrate the start of the 10th World Championship Tennis (WTC) playoffs, tournament officials screened a film of highlights from the previous nine WCT Finals. They wanted to underscore the prestige of this Dallas shootout conceived by WCT Directory Lamar Hunt as a kind of eight-man Super Bowl of pro tennis.

Unhappy for those who read between the frames, the film was a reminder that the WCT Finals used to be important and special, as well as rich. Not so in 1980.

The concluding tournament of "A Decade in Dallas," which was the title of the film, has been lamentably weak.

It should have a suitable stirring title match on Sunday when defending champion John McEnroe and the 1977 champ, Jimmy Connors, engage in a best-of-five-set duel for a $100,000 first prize. Nevertheless, this year's WCT final will be remembered mostly as much ado about nothing since the supporting cast was so undistinguished.

Instead of the "exceptional eight" of years past, this field could have been labeled the "ordinary octet," save for McEnroe and Connors. Consequently, the tournament that usually is referred to simply as "Dallas" turned out to be Dullsville.

It wasn't always that way, as the highlight film reminded us.

There was Ken Rosewall, compact andd classicly elegant, torpedoing the unsinkable Rod Laver for a $50,000 top prize, almost unthinkable at that time, in the inaugural WCT playoff in 1971. This was a memorale milestone for the pro game, proving that it had gone big time.

There was an exhausted Rosewall, somehow summoning two vintage backhands to win a fifthset tie breaker and beat Laver again in the 1972 championship, one of the greatest matches ever played.

There was Stan Smith in 1973, confirming his brief standing as the world's No. 1 player by outgunning Arthur Ashe, claiming a title that he considered more important than his 1972 triumph at Wimbledon because he had to beat a stronger field.

There was John Newcombe, at the peak of his powerful form in 1974, capturing a prize he had stalked for nine months by beating a surprised finalist: a teen-age prodigy named Bjorn Borg.

There was Ashe in 1975, his greatest year, beating Borg in Dallas two months before gaining more glory at Wimbledon.

There was Borg in 1976, flogging whipping boy Guillermor Vilas to win his first big indoor title two months before he took over his Wimbledon champion.

There was Connors, the only one of the decade's top players who had ignored Dallas, entering for the first time and winning in 1977.

There was Broadway Vitas Gerulaitis, winning in 1978 after Borg defaulted with an infected thumb.

And there was McEnroe establishing himself as part of the triumvirate at the pinnacle of the game last May by zapping Connors in the semis and Borg in a rousing final.

Sunday's McEnroe-Connors battle on a medium-pace synthetic court a the new Reunion Arena promises to be a rugged, flat-out fight, as their three previous meetings this year have been. Connors has won two of them.

"There's pressure because of the fact that we're ranked Nos. 2 and 3 in the world. We're fighting for tht spot," says McEnroe, 21. "The head-to-head record is kind of important after a while."

Says Connors, "There are some matches between certain players that bring out the best in the crowd and the best in the players, and my matches with McEnroe have been that kind. We have different styles, we're both capable of playing great tennis, and we go out there prepared to kill each other to win. I think the people enjoy that kind of tennis."

True enough. The intramural skirmishes among the Borg-McEnroe-Connors troika are the best spectacles in the game today.

What is troubling is the inescapable conclusion that this year's WCT playoffs really boil down to a one day tournament, a challenge match between McEnroe and Connors. Borg and the rest of the world's top 10 players did not bother to try to qualify for Dallas, a sad commentary on the present state of men's tennis.

Borg played in one of the eight WCT-promoted Grand Prix tournaments that qualify the top eight point earners for Dallas. Gerulaitis played four, but approached them indifferently. Ditto Vilas. Gene Mayer played two; Eddie Dibbs four; Roscoe Tanner, Victor Pecci and Jose Higueras, two each. So much for the current top 10, who found plenty of lucrative opportunities to play tournaments and exhibitions elsewhere.

The six players who joined McEnroe and Connors in Dallas were imposters: Ivan Lendl, ranked No. 13; John Sadri, No. 18; Bill Scanlon, No. 25; Johan Kriek, No. 28; Vijay Amritraj. No. 32, and Heinz Gunthardt, No. 33.

These are all attractive young players with appealing personalities and considerable promise, which is how WCT tried to sell them: "The wave of the future." But berths in the Dallas finals should be a reward for accomplishment, no potential.

The Dallas public, which bought a record number of tickets far in advance, expecting a stronger field, also set a new pro tennis record for no-shows. On opening night, 15,000 tickets were sold but only 7,000 spectators appeared to watch a quarterfinal match between Sadri and Kriek. No wonder. "At Wimbledon, this would be a first-round match," sniffed on indignant patron. "On court 12."

Lamar Hunt, who is almost as heavily into pro sports as his brothers are into the silver market, will not stand idly by much longer as his pet hometown tennis showcase sinks into second-rate status.

The word through the tennis grapevine is that he will try again next year under the present system, whereby his eight WCT qualifying tournaments form a subcircuit within the year-round Volvo Grand Prix series. If the players don't show more interest in reaching a $250,000 Dallas showdown, Hunt might thereafter pull out of the Grand Prix and declare a new war in pro tennis by signing players to contracts in competing head to head against the Grand Prix, as was the case in 1971-1972.

Pro tennis doesn't need more infighting. Its endless season is fragmented and confusing enough as it is. The casual fan is bewildered by the number of tournaments and exhibitions, all of which seem to run together in an endless road trip highlighted only be a few events of stature such as the French Open, Wimbledon and the U.S. Open.

Tennis needs order, and it needs true showcase events. The WCT Finals should be one of them. The foundation is there. You could look it up on the highlights film.