Knock, knock.

"Who's there," said George Washington University basketball coach. Bob Tallent responding to the banging on his office door at Smith Center not long ago.

"Walt Szczerbiak," said Walt Szczerbiak. "Get yourself out here on the court, Tallent. We're gonna play some ball."

Tallen - who played with Szczerbiak at GW in 1969 and helped coach him in 1971 - expected to see the same not-so-quick forward who never could "jump over a pencil" or shoot from beyond 10 feet. In short, the Szczerbiak who averaged 22.9 points for GW in 1971 on little more than hustle.

Instead, he saw a quick, fluid, 6-foot-6, 218-pound machine with moves a little like Julius Erving and a 25-foot jump shot a little like Rick Barry's.

"Good Lord, Walt," said Tallent, "where have you been and what the hell's happened to your game?"

What he heard was a long and happy story, the tale of one man who fled the meat grinder of American pro basketball to find happiness, fame and a small fortune in Madric.

If you ask Szczerbiak what he is doing these days, he gives an embarrassed laugh. "I guess," he says, "you'd have to say I'm the Dr. J. of Europe."

In fact, Szczerbiak is arguably the best professional basketball player in the world outside the NBA, although he is almost unknown in America, even at his alma mater.

In three seasons with Spain's perennial pro powerhouse, Real Madrid, Szczerbiak has averaged 33 points a game, shot an amazing 65 per cent, off the continent's dead backboards and led his team to the European Cup in 1974 and the Intercontinential Cup in 1976.

The Intercontinential Cup brings together the best teams from Europe, South America, Africa and Russia, and is considered the world championship outside the U.S.

Moving in these circles, playing one week in Tel Aviv and the next in Moscow. Szczerbiak who speaks fluent English, Spanish and Ukranian - proudly calls himself "a citizen of the world." And a well-known one.

On the streets of Madrid or Paris he is likely to be stopped for his autograph. Just as the great soccer player Pele would never sign his real last name (Orantes) if he were stopped on Fifth Avenue, so Szczerbiak goes by his nickname, "Walt."

"'Walt' is all I have on my uniform and that's all I sign," Szczerbiak chuckled. "They have even more trouble with my name there than they did in the states. I've given up on Szczerbiak. Walt is as unusual a name there as Pele would be in the U.S."

It is a singular road that Szczerbiak has traveled to an almost tax-free $35,000 salary, a free Madrid apartment overlooking a snowcapped mountain and fame at 27 years of age.

Four year ago Szczerbiak was disillusioned with the sport he had loved since he was 13. He was ready to quit and "look for honest work."

"One per cent of the kids who love basketball become high school stars. One per cent of those become college stars and one per cent of those become NBA stars," said Szczerbiak. "It's a brutal winowing out process full of injustices.

Pro basketball gave Szczerbiak the classic heart-breaking run around.

The Phoenix Suns drafted him in the third round in 1971. After a sparkling rookie camp they told him he had a 90 per cent chance of making the team. Szczerbiak took their word and bought a house in Arizona. In veterans camp he seldom played and was cut before the season. "My first lesson in broken trust," he said.

The Pittsburgh Condors of the ABA picked him up, but a cast of forwards "with ego problems" kept him from touching the ball often.

When Pittsburgh folded, Kentucky of the ABA picked him up in the 1972 despersal draft, but a roster full of big-name players with no-cut contracts led to his being released again. Szczerbiak sank to the basketball bushes, the Eastern League, where he was second-leading scorer.

By the summer of 1973 Szczerbiak had found his true game. "My baby fat disappeared. I was quicker than ever and suddenly I had an outside shot to go with the inside moves that had been my whole game all my life."

In the high-powered New York City Rucker League Szczerbiak played on the same team with Erving and led the club in scoring, averaging 32 a game. "I took that summer league very seriously," said Szczerbiak. "Once you've left the mainstream of basketball, the publicity and the all-America build-up, after one year, you're forgotten. It's brutal."

Off his Rucker stats, Buffalo offered Szczerbiak a one-shot, one-year NBA contract. Madrid offered a five-year, no-cut pact.

After long thought, Szczerbiak and wife Marilyn pulled up roots and headed for Spain. "It was like a magic transformation of my luck," said Szczerbiak. "In my second game with Madrid, I scored 47 points against our archrival Barcelona, and we beat them by a million. I haven't been able to do anything wrong since."

Szczerbiak has had NBA offers but he won't be returning. He has been exposed to a broader, more sensibly paced life than the NBA with its exhausting 100-game season can offer.

"In Europe I have seen so many different ways to live and to live happily," he said.

He and his wife spend their summers living in the basement of his in-laws' home on Long Island. "It's cool in the basement and we can save money," he said. "Three of my close relatives have been laid off their jobs and they need a little help."

In the winter he returns to stardom in Madrid. "If I could somehow transmit a feeling for the life I have in Europe to some of the friends who helped me a few years ago," mused Szczerbiak. "If they want to think of me, let them think of me taking a siesta."