Wimbledon champion Bjorn Borg and Vitas Gerulaitis, whom Borg has conquered in all eight of their career confrontations, are the critics' choices in the $200,000 World Championship Tennis (WCT) finals beginning tonight.

But perhaps the most pumped-up participant is the one who least expected to be here: Brian Gottfried.

"This tournament never entered my plans. I planned to take three weeks off in May and prepare for the European circuit," Gottfried said. THe unassuming, 26-year-old Floridian played only four of the eight WCT-promoted "Super Grand Prix" tournaments that qualified the top eight point-gatherers for this prestiguous playoff.

"One day last month I was on the phone to the WCT office, and a secretary asked me if I was going to play in Dallas if I qualified. I started laughing," he recalled.

"I asked where I was in the standings, and she said ninth, 20 points out of seventh. It was like a new year. I got really excited."

He went to Houston the following week, played well, and beat Ilie Nastase in the final of a $175,000 tournanment at the River Oaks Country Club. That tied him for seventh in the final standings with defending champ Jimmy Connors - who declined his invitation, as did Sandy Mayer.

Gottfried, a diligent if unflamboyant player, was elated to get a ticket back to Texas, where he majored in tennis at Trinity University in San Antonio. (He and Dick Stockton led Trinity to the NCCA Championship their senior year, 1972.)

"It's a windfall, a chance to play another major tournament," said Gottfried. "Now that I'm here, I'm really psyched up."

Gottfried has never played in the 8-year-old WCT finals. Last year he played the Colgate Grand Prix instead of the rival WCT tour; this year the two were merged into one series of tournaments.

Gottfried finished second in the 1977 Grand Prix behind Guillermo Vilas, and established himself solidly among world class players, just a shade behind the ruling troika of Borg, Connors and Vilas.

Gottfried will play the only other newcome to WCT boss Lemar Hunt's Texas-flavored shoot-out, Italian Corado (Little Soldier) Barazzutti, on Thursday.

Borg will opposed Stockton, runnerup to Connors here last year, in tonight's opener at Moody Coliseum on the campus of Southern Methodist University. The tournmanet will use a standard single-elmination format with all matches best of five sets.

Gerulaities, on leave from the World Team Tennis New York Apples, will Raul Ramirez tomorrow evening. The first round will conclude Thursday with Nastase against Eddie Dibbs, who beat him in an acrimonious match here last year, and with Gottfried against Barazzutti.

Borg, erstwhile, "Teen Angle" who will turn a hoary 22 later this month, was runnerup to John Newcombe in 1974, to Arthur Ashe in 1975, and beat Vilas in the final here in 1976.

He did not defend last year, opting just before the season started to play the Grand Prix instead of the WCT circuit. WCT sued him for alleged breach of contract and the case was settled out of court last fall. One of the provisions was Borg's promise to play a number of WCT events this year.

But who would recognize pro tennis if everything were harmonious and agreeable? This time Connors decided not to defend, for reasons best known to him and mother-manager Gloria Connors.

Connors went to Rotterdam early last month and won a tournament to qualify for Dallas, but shortly thereafter Mrs. Connors cabled WCT that Jimmy would not participate because of previous commitment to play exhibitions.

Connors had assumed, as Gottfried did, that his limited schedule of tournaments would not enable him to qualify. He played no two events - the U.S. Pro Indoor at Philadelphia and Rotterdam - but won them both.

He apparently planned to play, but a mysterious dispute with WCT officialdom - not an unfamiliar phenomenon for Connors - developed. His status became a moot point when Connors subsequently developed mononucleosis, which hospitalized him in Los Angles until last weekend and will keep him out of action several more weeks.

Mayer, who won the St. Louis tournanment and finished sixth in the standings, declined because he did not have release from his contract with the World Team Tennis Golden Gaters.

Gerulaitis, winner in Richmond (where he also accumulated $2,700 in fines for bad behavior), topped the standings. Borg, victor in two of the five tournaments he played (Birmingham and Milan), was second, followed by Ramirez (Monte Carlo champ), Dibbs, Nastase, Mayer Gottfried, Connors, Stockton and Barazzutti.