In the latest semiweekly computer rankings of the Association of Tennis Professionals, based on tournament performance over the past 12 months, there is one name whose exalted position is bound to surprise all but the most astute followers of the game.

The ninth-best player in the world, ahead of Sandy Mayer and Harold Solomon, Roscoe Tanner and Ilie Nastase, John McEnroe and Dick Stockton, is the man they call "The Little Soldier": Corrado Barazzutti of Italy.

"He may be the most underrated player in the world because his game doesn't look like much," says Arthur Ashe, who was a TV commentator at the Alan King Classic at Las Vegas the week before last, when Barazzutti got to the final before defaulting to Solomon because of food poisoning.

"He just keeps getting the ball back, sometimes with so little pace and spin, coming at times to the foreas it floats through the air. It's tough to outsteady him, but when you try to attack and go to the net behind anything but a good approach shot, his passing shots can make you cry."

Barazzutti, 25, looks undernourished at 5-foot-9 and 141 pounds, but he lifts weights to build up strength. He is best on clay courts, but has adapted well to other surfaces, varying pace and spin, coming at times to the forec-court which was formerly alien and terrifying territory for him.

"After many tournaments on cement and indoors on carpet surfaces, I start to play better because I must," he said yesterday, after working out on the medium-slow Supreme Court at Moody Coliseum, where he plays Brian Gottfried tonight in the $200,000 World Championship Tennis (WCT) Finals.

Barazzutti is a little bit like Solomon - quick afoot, in excellent condition, exceedingly determined and willing to run all day to grind down an opponent. He ran smack his ground strokes and is usually less a "pusher" than an attacking backcourt player.

Barazzutti does not have the sloe-eyed good looks, the matinee idol physique and urbanity of his dashing countryman, Adriano Panatta. He has been aptly described as "ferret-faced," and resembling "a war waif, a little Italian boy who might ask G.L. Joe for some chocolate."

He does not adorn as many posters or magazine covers as Panatta, whose victories in the 1976 Italian and French Open assured him financial security for life, but he practices much more diligently. And now he is ranked No. 1 in Italy.

"Rivalry? No, I don't think so," says Barazzutti, who a few years ago barely spoke to Panatta, so intense was the professional jealousy between them. Having traveled the pro circuit for several years together, they get along now. But Barazzutti is comfortable with his new, esteemed position.

"I am No. 1 because I played better than Adriano," he says. "For me it is very important to be in the first 10 in the world. Two years ago I was No. 60. Now I am No. 9. It's very good, but I want to go more up, to the first five."

The son of a poor truck driver, Barazutti was born in Udine (pronounced OO-dee-nay), in northeastern Italy, in an area called Friuli, settled in the second century by invaders from the north.

"They are very tough, hard-working, self-sufficient people in this region. Two years ago they had a very bad earthquake, but they did not weep. They just started to build again," says Gianni Clerici, a former Davis Cup player who is now a noted novelist, playwright and columnist for II Giorno in Milan.

"If you ask Corrado about these things, he does not know. But I think the ethnology is important in understanding him. People in Italy did not expect him to be better than Adriano, but those who knew tennis did, because they saw what he was doing very young, with just a forehand and backhand, legs and a brain. He made results by hard work."

At age 7, Barazzutti moved to Alessandria, a 16th-century city on the River Po in northwestern Italy, and started playing tennis under the tutelage of Giuseppe Cornara, who is better known as a soccer coach.

Barazzutti won the age 14, 16, and 18 championships in Italy, and in 1971 captured the prestigious Orange Bowl at Miami, beating Vitas Gerulaitis in the final.

The following year he started playing Davis Cup and enhanced his reputation as a lion-hearted fighter, always scrambling and battling. He thinks his most important victory came over Jaime Fillol, after a horrendous start, in the opening match of Italy's 4-1 victory over Chile in the 1976 Davis Cup final at Santiago.

Last year, after recovering from a broken ankle, Baruzzutti reached the semifinals of the U.S. Open, dispatching Nastase and routing Brian Gottfried before losing a tough match to Jimmy Connors. Earlier he had won a WCT tournament at Charlotte, blasting Panatta in the semis and Eddie Dibbs in the final, and the Swedish Open at Baastad.