The question, quite simply is who is the No. 1 man in tennis for 1977? Guillermo Vilas or Bjorn Borg?

The tournament that should supply the answer, one week into the New Year, is the $400,000 Colgate Grand Prix Master Championship, which begins Wednesday and runs through Sunday at Madison Square Garden in New York.

The tournament has been around since 1970 - played each December in such exotic spots as Tokyo, paris, Barcelona and Melbourne - but it has been given greater impact and U.S. television exposure with a massive influx of money from first-year Grand Prix sponsor Colgate-Palmolive.

What truly distinguishes this year's Master, however, more than the extravagance that makes it the richest tournament of the year, is the quality of the field: Vilas, Borg, Jimmy Connors, Manuel Orantes, Brain Gottfried, Roscoe Tanner, Eddie Dibbs and Raul Ramirez.

Among them they have won all of the world's major titles this season, with the exception of the Italian Open (won by Vitas Gerulaitis). Consequently, the Masters is what it has always aspired to be: "the championship of champions."

Morever, the question of the No. 1 world ranking - an honour as unofficial mythical, but nevertheless widely-sought as the No. 1 national ranking in college football - is squarely on the line.

Vilas prematurely declared himself No. 1 for the year back in September, after winning the last of the traditional Grand Slam events, the U.S.Open, Ilis reasoning: 'I win two of the Big Four, the French and Forest Hills, and am runner-up in the Australian, so automatically I am No. 1."

It is not quite that simple, even though Vilas is coming off the most impressive six months in the 10-year "open tennis" era. He has won 12 of 13 tournaments, 76 of 77 matches, since the beginning of July. His only loss came the first week in October to four-time Masters champ Ilie Natstase at Aix-en Provence, France. Villas walked off, trailing 2-0 in sets, to protest the Romanian's use of the now-banned 'double-strung' racket.

But Borg won the biggest tournament of them all. Wimbledon, and beat Vilas the only two times they played in 1977: in the finals of a Grand Prix tournament at Nice and in the semifinals of a World Championship of Tennis (WCT) event at Monte Carlo on successive weekends in April.

Vilas' singular domination of the last six months cannot erase those springtime losses.

Last year Borg was bitterly disappointed when the No. 1 a ranking went to Connors, even though Borg had won the WCT Finals at Dallas and Wimbledon, and was runner-up in an excruciating final at Forest Hills.

'Whoever wins Wimbledon is always ranked No. 1. How can Bjorn not be?" snorted Lennart Bergelin, Borg's coach, undoubtedly reflecting his man's ire. But Borg was 0-4 in head-to-head meetings with Connors in 1976, and that is what cost him the No. 1 vote.

The same rationale aids Borg's cause this year. Coming into the Masters, he is 2-0 over both Vilas and Connors (finals of the Pepsi four-man last January and Wimbledon). Only a loss to Vilas in a showdown next week could cost him the top spot.

Connors, meanwhile, won the 1977 WCT Finals, and was runner-up at Wimbledon and Forest Hills, but didn't win any of the Grand Slam events and is 0-2 against Borg and 0-1 events and is 0-2 against Borg and 0-1. He is the top player of the last four years, surely, but cannot realistically claim to be No. 1 for 1977, even if he beats both Vilas and Borg and wins the Masters.

Borg has not exactly been a slouch the second half of the year, either. He played World Team Tennis for the Cleveland-Pittsburgh Nets and did not complete in a tournament between Wimbledon and Forest Hills, where he defaulted to Dick Stockton in the fourth round with a shoulder injury. Since then he has won five of six tournaments, 29 of 30 matches.

Going into Wimbledon, Borg had won three consecutive tournaments (including Nice and Monte Carlo), so he had won 53 of 54 tournament matches before being upset by Sherwood Stewart in the third round of his last outing, at Oviedo, Spain, the week of Nov. 21.

On the year, Vilas has won 18 of 32 tournaments he has played; Borg has won nine of 17; Connors six of 16.

For the Masters, the eight players are divided into two groups for three days of round-robin play, each man playing the other three in his group.

The top two in each group advance to the semifinals, No. 1 of the "Red Group" playing No. 2 of the "Blue Group," and No. 1 of Blue playing No. 2 of Red.

The semifinal survivors then play for the top prize of $100,000. The runner-up gets $64,000.

Vilas, Connors, Dibbs and Orantes (who beat Wojtek Fibak in last year's final at Houseton, the last year the Grand Prix and Masters were sponsored by the Commercial Union Assurance Co.) make up the "Red Group." Vilas and Connors will meet Thursday night in a rematch of the epic U.S. Open final that Vilas won, 2-6, 6-3, 7-6, 6-0.

Borg, Gottfried, Tanner and Ramirez comprise the weaker but still formidable "Blue Group." (The grouping is determined by final standigs in the Grand Prix.) Borg therefore cannot meet Vilas or Connors until at least the semifinals.

The tournament will be played on a medium-slow synthetic surface that should be equally suited to teh heavy topspin groundstrokes of Vilas and Borg and Connors' flatter, riskier, lower-over-the-net shots.

There is also a four-team doubles playoff, with a straight "knockout" format, $40,000 to the winning team, $20,000 to the runners-up, $10,000 to the first-round losers. The pairings are Gottfried-Ramirez vs. Stan Smith Bob Lutz and Bob Hewitt-Frew MeMillan vs. Sherwood Stewart-Fred McNair IV or John Alexander-Phil Dent.

Vilas has already claimed a bonus of $300,000 - up from $150,000 a year ago, when Ramirez won, and from 25,000 in 1970, when Cliff Richey captured the inaugural Grand Prix - for topping the standings. He only has to show up to claim it.

Vilas is also the only top name who has not signed up for next year's restructured Grand Prix - highlighted by 33 "super tournaments" of at least $175,000 apiece - which will offer a $350,000 top bonus prize. He reportedly has balked at regulaltions strictly prohibiting the payment of "appearance money" in Grand Prix events.

Vilas complained about the moving of the Masters to January when he arrived in New York last week. "I come only to collect the $300,000. Otherwise, I wouldn't be here. This is the 1977 Masters and shouldn't be played in 1978," he said, arguing that the scheduling interfered with the players' celebration of Christmas and New Year's and took away a logical rest period. He has not played since winning the South African Open the first week in December.

Vilas obviously does not understand the complexities of TV scheduling. The Masters assumed its current date so that it could be on commerical television nationally the weekend between the National Football League conference championship games and the Super Bowl. CBS will televise portions of the semifinals next Saturday (WTOP-TV 9, 3-4:30 p. M.) and the finals on Sunday (4-6 p.m.). For Colgate, TV and money talk.