Walton was born into a nonsporty family in San Diego. His father was a social worker, his mother a librarian. As a boy, Walton had such a severe stutter that he preferred not to speak. He learned to express himself, instead, through experi­ences: riding his bike, running around at the beach, reading and then — transformatively — playing basketball. He played all day, all over San Diego. Even as a boy, before his height was anything special, Walton was formidable. He sometimes says he peaked at 12.

But the injuries started early, too. At 14, Walton blew out his knee in a pickup game. It was during his recovery from that injury, while he lay in bed for three months, that Walton hit his improbable growth spurt: He got in bed at 6-foot-1 and got out at 6-foot-7½. This is one of the many ways in which Walton’s basketball life seems mythological: The injury and the growth, the gift and the curse, were one. Walton’s sudden height opened up a whole new realm of command. As a high-school senior, Walton made nearly 80 percent of his shots and averaged 25 rebounds and 12 blocks a game.

He was recruited by John Wooden to join mighty U.C.L.A., taking up the center position of Lew Alcindor (soon to be known as Kareem Abdul-Jabbar), who had recently graduated. By some measures, Walton was just as good at U.C.L.A. as Kareem. His team won 88 games in a row, still a record, including two national championships, and Walton won the college player of the year award all three years he was eligible for it. In the 1973 N.C.A.A. final, Walton made 21 of his 22 official shots on his way to 44 points. Even then, his knees were almost too bad to play on; every game required an elaborate regimen of icing and heating, and often he was in too much pain to practice.

Despite his injuries, Walton was the No. 1 pick in the 1974 N.B.A. draft. He went to one of the worst teams, and the smallest market, in the league: the Portland Trail Blazers. Walton’s long red hair flew behind him as he ran, and a scraggly red beard nested on the bottom of his face. (The only thing that Walton cared about in his first N.B.A. contract was control over his grooming.) In his prime, Walton was the human embodiment of the beauty of the sport. Watch the old footage: He looks like a basketball textbook come to life, crouching deep in his defensive stance, arms spread wide, leaping instantly to block a shot, then leaping up again to grab the rebound, then turning and firing a perfect pass up the floor to his guards. On offense, Walton demanded the ball with the enthusiasm of a know-it-all raising his hand in class: Here, here, the answer is here.

But Walton dominated in a social way. His signature gesture, in those years, was to run down the court with both arms high in the air, twirling his hands around each other like an eggbeater. The action seemed almost mystical — an invocation of the great swirling energy of life — and it would send Walton’s teammates swirling around him until, more often than seemed likely, he would find one of them wide open for a layup. He was never a high scorer, but he was probably the best-passing big man in the history of the game. He blocked shots not out of bounds but directly to his teammates; he became famous for throwing outlet passes to start his team on a fast break before he had even come back down to the floor from getting a rebound. For a couple of magical years, the Blazers were a joyful unit, the epitome of unselfish teamwork, and they radically overachieved because of it, improbably winning the 1977 championship over Dr. J and the star-studded Philadelphia 76ers. In the final game of the series, Walton had 20 points, 23 rebounds, 7 assists and 8 blocked shots.

But just then, at the height of it all, when the defending-champion Blazers looked set for perpetual glory (they started the next season 50-10), Walton was struck by injury again. He tried to return for the playoffs, his foot loaded up with anesthetic, but a crucial bone split as he ran down the court. There were lawsuits, recriminations, burned bridges, bad blood. There were comebacks that ended in further injuries. Walton was 24 when he won the championship; before he even turned 30, doctors told him they had abandoned hope of saving his basketball career — their new goal was to make sure they wouldn’t have to amputate his feet.