Over the years, tennis players have spoken with reverence and awe about their debuts as Davis Cup singles players, the trembling and jitters that the approach of the moment occasioned.

Romanian Ilie Nastase gave this heartfelt description of the peculiar pressures of representing one's nation in the grandaddy of international team competitions:

"Every shot you miss is going straight to your heart, killing you, because you are trying so hard and the people want so much for you to win. You are not uptight for yourself, like in a tournament. You are uptight for your team and your country."

John McEnroe, 19, gets his proverbial baptism of fire Friday in the opener of the best-of-five-match final between the United States and Great Britain, at Mission Hills Country Club, but he seems to have nerves of asbestos.

Winner of two tournaments in the last month, the brash and seemingly unshakable lefthander from Douglaston, N.Y., was drawn today to play Britain's John Lloyd in the first match of the three-day series that will determine for the 67th time possession of the sterling punch bowl symbolic of worldwide team supremacy in tennis.

"I was a nervous wreck before my first Davis Cup singles in Mexico in 1976. I couldn't sleep the night before. But John is a different individual. He doesn't seem intimidated by anything," said Brian Gottfried, who will play British ace Buster Mottram in Friday's second singles.

"It's been that way since he started playing pro tournaments. Look at what he did at Wimbledon in 1977," added Gottfried, 26, referring to the then 18-year-old McEnroe's charge through the qualifying competition and into the semifinals, the only qualifier and youngest man ever to get that far in the world's most prestigious tournament.

McEnroe also reached the semifinals of the U.S. Open in September on hard courts similar to those at Mission Hills, thereby becoming the first man since Ken Rosewall in the 1950s to reach the semifinals of both Wimbledon and the U.S. championships as a teen-ager.

McEnroe said before a final practice session on the medium-slow cement courts here that it didn't matter to him whether he played first or second.

"You have to play each of the singles players on the other team, so the order isn't any big deal," he shrugged.

But Tony Trabert, trying to end three years of frustration as the U.S. captain 23 years after he last played in the Davis Cup, was pleased with the pairings.

"I like the idea of John playing first, so he doesn't have to sit around half the day thinking about it," said Trabert. "This way he'll get up, have breakfast, have a hit and a rubdown and bingo, they'll ring the bell.

"The kid doesn't show any jitters. He's obviously from a different mold. He was loose as a goose in the dressing room today, reading a story about himself in Sports Illustrated. But he's got to be a little nervous when the time comes.

"That's like asking a soldier if he's nervous when he hits the beachhead," continued Trabert, who compiled a 278 record in singles and doubles as a Davis Cup player between 1951 and 1955. "If he says no, you better check him, because he's not playing with a full deck."

The draw ceremonies were conducted by Francisco (Pancho) Contreras of Mexico, the neutral referee, and International Tennis Federation President Philippe Chatrier of France at the 5,000-seat tennis stadium in this town outside Palm Springs. A cold snap hit this week, sending evening temperatures into the 20s for the first time in two decades.

Trabert named veterans Stan Smith and Bob Lutz, and British captain Paul Hutchins selected David Lloyed (John's brother) and Mark Cox, for Saturday's doubles match. The captains have the option of changing their doubles pairings an hour before the match.

Smith -- 15-5 in singles, 16-2 in doubles in nine years on the U.S team, and who teamed with Lutz to clinch the cup in 1968-69-70 -- twisted his ankle in practice today, but is expected to play. "It is a little discolored, but not swollen. It feels okay." said Smith, who seemed unencumbered by the injury as he skipped rope and worked out today.

McEnroe will play Mottram in the fourth match Sunday morning, with Gottfried facing John Lloyd in the finals.

The Public Broadcasting Service is televising the matches nationally. WETA-TV-26 in Washington will carry taped highlights of first-day action from 10 p.m. to midnight Friday, taped singles highlights and the doubles match live Saturday at 2 p.m., and the final singles live Sunday at 2 p.m.

McEnroe has never played either of the British men in singles, and Gottfried is 1-0 against Mottram and 2-2 against Lloyd in previous meetings, but the U.S. is heavily favored to win the cup for the first time since 1972.

The U.S. last reached the final in 1973, and was beaten, 5-0, by Australia at Cleveland. The last four years -- two under previous captain Dennis Ralston, two under Trabert -- the U.S. failed to get through the American Zone preliminaries, falling to Colombia in 1974, Mexico in 1975-76, and Argentina last year.

This season, with Harold Solomon, Vitas Gerulaitis, Gottfried and Arthur Ashe taking shifts as singles players and Sherwood Stewart-Fred McNair, IV, Gottfried-McEnroe, and Smith-Lutz assuming the doubles responsibilities, the U.S. beat South Africa, 4-1; Chile, 3-2 and Sweden, 3-2.

The Americans, as so often in recent years, are without their top guns: Connors, who has rejected repeated entreaties from Trabert to join the U.S. effort and is in Switzerland playing exhibitions, and Gerulaitis, who wanted to play but could not escape a prior contractual agreement to play in Germany. McEnroe and Gottfried are among the top 10 players in the world, ranked well above Mottram and Lloyd.

The British, in the final for the first time since they relinquished the cup to the U.S. in 1937, have trained hard for this match. They arrived here 10 days ago to acclimate themselves to a surface that is more familiar to the Americans, but not a major advantage to either side.