Most Italians had never heard of Victor Amaya until yesterday, when the hulking, 6-foot-7, 220-pound left-hander from Holland, Mich., squashed their top-ranked player, Corrado Barazzutti, in the first round of the Italian Open tennis championships.

Even those aficionados who recognized the name, and remembered that Amaya had made two undistinguished previous appearances at Foro Italico, knew little about him. But they came intensely interested as he served mightily, despite numerous double-faults in the wind, and blanketed the net for a 6-3, 7-6 triumph over the strangely docile Barazzutti.

"We must talk to him," said one Italian hournalist," and ask him, 'Who are you, Mr. Amaya? Are you the son of King Kong?"

Amaya - whose grandfather was Mexican and who has been likened in appearance to "the Chief" in the movie, "One Flew Over the Cuckoo's nest" - plods around the court in his size-15 tennis shoes, pulverizing serves and volleys with atomic force but backing them up with little in the way of ground strokes and the more subtle elements of the game.

Seemingly undeterred by the partisan, vocal crowd that is so much a part of matches between Italians and foreigners on the "campo centrale" (center court) here, Amaya attacked from the outset, dictated the tactics and admirably kept his wits about him after squandering five match points.

"I've had lots of close matches against players ranked in the top 10 in the world, but had never beaten one, he said. "Barazutti's a much better player than I am nine days out of 10, but I thought if I could get on top of him early I'd have a chance."

Deafening roars reverberated through the majestic marble arena as Barazzutti, "the little soldier" who has supplanted Adriano panatta as the No. 1 man in the Italian tennis rankings, if not the hearts of his countrymen, saved two match points on Amaya's serve at 6-5 in the second sets, and three from 3-6 in the decisive tie breaker.

Panatta had ridden the crowd's adoration back from 0-5 in the first set and 3-5 in the second to outst defending champ Vitas Gerulaitis on Monday, and now the natives sensed that another of their heroes was going to escape dire peril.

But though the sun was smiling brightly - a few hours later, appropriately, the sky turned gray and raindrops fell - it did not shine on Barazzutti.Crunching Amaya smash put him ahead again in the tie breaker, 7 points to 6, and he clutched this sixth match point with another big serve and piercing backhand volley.

Barazzutti, 25, was seeded No. 7. One other seed, No. 6 Raul Ramirez, the champion here in 1975, also fell to a big man who blisters the ball.

Dick Crealy, the erratic 6-4 Australian, won only six points in the first set, then got his act together to erase Ramirez, 0-6, 7-6, 6-3.

No. 5 seed Manuel Orantes, the graceful Spanish left-hander who won here in 1972 and was runner-up in 1973 and 1975, withdrew because of muscle spasms in his back.

Australian John Newcombe, the champion of 1969 who is seeded No. 10 this year, survived one of the shaky spells that have characterized his as yet unimpressive comeback and beat Tom Gullikson, the left-handed and lower ranked of the identical twins, 7-6, 6-1.

But this day belonged to Amaya, who had won only one match in two previous appearances on the slow, red clay of Foro Italico, beating Frenchman Francois Caujolle in the first round in 1976.

Surprisingly, he had played twice on the campo centale. "In 1976, they were really hard up for matches the first day, so they stuck me and caujolle out there. Last year I played Gerulaitis in the first round, but I wasn't out there very long."

Most people didn't expect him to last long yesterday, in the arena that can make foreigner's feel like Christians against the lions when they play an Italian.

"I was worried about it going in," the 23-year-old political science graduate of the University of Michigan said. "But I think the crowd helped me in the first set because he got nervous. They expected him to win, and it put a lot or pressure on him.

"But when I got ahead they started chanting for him to come back, it scared me. My heart was in my mouth."

The crowd was screaming and stomping at the end, but Amaya took a critical point on Barazzutti's serve with a thunderous overhead, and unleashed his last murderous serve and volley for the match.

"He's a very self-controlled fellow, young Victor," said Bertie Bowron, a bilingual Englishman who has been umpiring matches here so long most people think he is Italian. "He didn't let the crowd get to him. Just before the first game, when he went out to serve, he looked up at me and said "This is going to be a bit of fun isn't it?"