Mexico ran short on a 17-year-old''s miracles and a 27-year-old's energy tody when Roscoe Tanner and John McEnroe rallied the United States to a 3-2 victory in the first round of Davis Cup competition.

Tanner and his big serve swiftly disposed of Jorge Lozano, 6-3, 6-2, 6-3, in the first of the two singles matches, and McEnroe won the last match from Raul Ramirez, 6-4, 6-3, 6-0.

"I said Friday there'd be no excuse for losing to these guys," McEnroe said, "and I didn't want to have my sneaker in my mouth."

McEnroe will be joined by his old adversary, Jimmy Connors, when the United States plays in the second round, meeting Czechoslovakia the second weekend in July. Czechoslovakia won its first match, 3-1, over Switzerland. The site has not been determined.

In the deciding match today, Ramirez would ultimately show the affects of having played a 3-hour 52-minute singles match on Friday and a 3-hour 27-minute doubles match on Saturday. The first two sets turned on what might have been questionable line calls, but the third was simply a rout and gave Arthur Ashe a victory in his debut as U.S. captain.

Was Ramirez tired?

"Tired," he said, "of him hitting so many good shots."

"I tried to give him as few easy shots as possible," McEnroe said. "I could see him getting tired in the middle of the second set."

Ramirez also tired of McEnroe's complaining, which was not as prevalent as his reputation might have suggested.

"I think he complains too much," Ramirez said. "I don't think it's nice. When you're on the court, not too many players like it when the opponent complains. He's a great player, maybe he truly thinks all of his shots are in."

Today's most critical call, however, went against Ramirez. He was not particularly vocal in his protests, but he was obviously less than happy.

The first came at the end of the first set, Ramirez serving with McEnroe ahead, 5-4. Ramirez served at set point and McEnroe's deep return hit near -- or on -- the baseline to his right. It was called in, and McEnroe had the first service break and the set.

"I thought the ball was out," Ramirez said. "I thought that because I saw the mark."

At break point in the second set, with Ramirez serving, McEnroe hit a ball that landed either on or near a line. And once again it was ruled in his favor. He had a 5-3 lead, and held serve in a game which went twice to deuce to go ahead in sets, 2-0.

That was almost Ramirez's last hurrah. The first game of the third set went six times to deuce, the first four times the advantage going to Ramirez. He could not close it out and hold serve, however, and McEnroe won when Ramirez hit a tired forehand into the net.

Ramirez, physically drained, already, had to be emotionally drained as well and, as a fan yelled during the final game: "Adios Mexico."

For Tanner, it was vindication of sorts; he had lost the Friday match to Ramirez to help dig the hole that the U.S. escaped only late today.

"It's always emotional to play in the Davis Cup," Tanner said, "but I'm tired of us being behind. I'm ready to be ahead."

John McEnroe accomplished that.

"What I had to do," McEnroe said, "was save the country from embarrassing itself."