Only a few weeks ago he was bowing and blowing kisses at a ceremony in New York, telling a rapturous crowd: “I missed you.” Andre Agassi, revered as an elder statesman of tennis, was one of four sportsmen being honoured as “athletes who give something back”. And, boy, was he planning to give something back.

Agassi’s explosive revelations last week that he had used drugs and lied about it to save his career left tennis squirming, commentators apoplectic and the publishers of his autobiography rubbing their hands with glee. Was it revenge against the game he secretly “hated” and a violent father who drove him on remorselessly? And what did his wife, the respected former tennis champion Steffi Graf, think about his indiscretions?

The 39-year-old former world No 1 certainly does not need the money, as his old adversary Boris Becker pointed out. Agassi earned more than $30m in prize money during a career in which he won eight Grand Slam tournaments and a reputation as one of the greatest and most charismatic players of all time.

Once, teenage girls screamed when the young Agassi, sporting pink Lycra shorts, an earring and a bleach-blond ponytail, exposed his shaved torso, apparently unaware that baldness was approaching. He lied about that, too: his glorious mane was a wig through most of the 1990s. He lost the 1990 French Open worrying about it: “I prayed. Not for victory but that my hairpiece would not fall off.”

Much of the hand-wringing concerns Agassi’s admission that after a drug test proved positive, he contrived a false account of what he had done and the authorities let him off scot-free.

By his account of the episode in his forthcoming memoir, Open, extracts from which appeared in Britain and Germany last week, he snorted crystal meth in 1997, when his form was failing and he was having doubts about his impending marriage to Brooke Shields, the actress. “I think all the time about postponing it,” he wrote.

He had been introduced to Shields by a mutual friend, but the course of true love had hit an early obstacle in the form of the bride’s domineering mother. Teri Shields had argued bitterly with Agassi, who banned his future mother-in-law from his home in Las Vegas.

It was there that his assistant, identified only as Slim, offered him some “gack”, or crystal meth, with the promise that it would make him feel like Superman. Aware that he had crossed a “Rubicon” while snorting a line, Agassi experienced “a moment of regret, followed by vast sadness”, then “a tidal wave of euphoria”. He was seized by a desperate desire to clean the house and the belief that he “could do anything”.

This evidently included his marriage, for the event went ahead that April in the presence of guests such as Clint Eastwood, Kevin Costner and Neil Sedaka, who composed a song for the occasion. Yet two months later the couple were apart, Shields in Los Angeles and Agassi back in Las Vegas.

Professionally, Agassi was struggling. An injured wrist had forced him to pull out of tournaments in Paris and London and the addictive crystal meth kept him awake at night. One day that autumn his folly caught up with him when a telephone call from the Association of Tennis Professionals (ATP) informed the player that his urine sample from a recent tournament had been found to contain traces of crystal meth — a violation incurring a three-month suspension.

“My name, my career, everything is now on the line,” he reflected. “Whatever I’ve achieved, whatever I’ve worked for, might soon mean nothing.”

Days later he composed a formal response “filled with lies interwoven with bits of truth”, claiming that he had accidentally drunk a spiked soda prepared by Slim, a known drug user, whom he had sacked. His explanation was accepted.

Some believe that John McEnroe’s frank autobiography tempted Agassi down the path of making saleable revelations. On the face of it, the rebellious McEnroe could have been a model for Agassi: both players had pushy fathers and spindly physiques. (Agassi’s pigeon-toed gait was caused by spondylolisthesis, a condition of displaced vertebra with which he was born).

The comparison is rejected by Barry Flatman, the Sunday Times tennis correspondent: “Agassi played more like Jimmy Connors than McEnroe, but he and Connors despised each other in the early years. Agassi was touted as the best returner in the game, which Connors resented. When I first saw Agassi play he was about 20, I thought he couldn’t be an athlete. But he had unnatural hand-to-eye co-ordination that enabled him to hit the ball early on the rise.”

The gunslinger speed of Agassi’s returns was drilled into him by his father Mike Agassi, an Iranian of Armenian and Assyrian descent. He had represented Iran in boxing at the 1948 and 1952 Olympics before emigrating to the United States, where he married Betty.

Agassi was born on April 29, 1970, in Las Vegas, where his father worked as a security man for casinos and as a tennis pro at the Tropicana. Agassi’s elder sister married Pancho Gonzales, the former tennis champion, and Mike was determined to turn his son into an even greater tennis pro. To this end he set up an infernal machine known as “the dragon” that fired tennis balls at his seven-year-old son at 110mph. “I keep playing, keep hitting all morning, and all afternoon, because I have no choice,” Agassi wrote. “No matter how much I want to stop I don’t.”

The prospect of Mike chasing him around the house spurred him on. Mike, who liked to shoot hawks, was “violent by nature”, shadowboxed constantly (sometimes punching his wife in his sleep), and kept an axe handle in his car for dealing with recalcitrant drivers.

“I don’t want to upset him,” Agassi confides. “Bad stuff happens when my father is upset.” Yet he loved his father and was horrified by Mike’s habit of easing a stiff neck by hanging himself from his punchbag harness. So he stood in front of the spitting dragon, feeling “tiny” and “helpless” as Mike yelled at him to “hit earlier”. Soon he could hit a ball that had ricocheted off another: “I know there are few children in the world who could have seen that ball, let alone hit it.”

At 13 Agassi was sent to Nick Bollettieri’s tennis academy in Florida, which has produced a stream of winners. Mike could afford only an eight-week course but, after watching Agassi play for 10 minutes, Bollettieri took him on for free and became his mentor.

Agassi hit the tennis circuit among a new pack that included Pete Sampras, Michael Chang and Jim Courier. His eccentric clothing and brattish behaviour attracted a following, but not everyone was impressed. “I never warmed to him,” says Flatman. “I always found him difficult and insincere.” Others contrasted his posturing and blown kisses with his high-handed treatment of ball boys and autograph hunters (notably a crestfallen young Andy Murray).

At first Agassi struggled to win a big tournament. After boycotting Wimbledon for several years, apparently over its white dress code, he triumphed there in 1992. On his way to the final, in which he beat Goran Ivanisevic, he faced Becker in a closely fought quarter-final. He noticed that the German put his tongue out before serving. “When the tongue was in the middle, he was serving down the middle of the deuce court or into the body; when the tongue was off to one side, he was serving out wide.”

By 1997 Agassi had won two more Grand Slam titles. He had looks, money and a beautiful wife, but his marriage was foundering and drugs played a part in his fall from the top of the rankings to a low point of No 141. Then, in a remarkable reverse, his epic fitness campaign in the desert of Nevada paid off. In 1998 he made the biggest jump into the top 10 in the history of the ATP rankings, climbing to No 6. He ended the following year as No 1.

His romance with Graf persuaded many critics that she had spotted hidden qualities in the self-regarding player. Their spark kindled during the champions’ dance after the 1999 French Open, in which they were both surprise winners. Once again Agassi had to surmount parental problems as the pugnacious Mike squared off to Graf’s father, Peter, who had spent two years in jail for tax evasion. The couple, who married in 2001, have a son, Jaden, 8, and a daughter, Jaz, 6.

Tormented by back pain, Agassi played his final US Open in 2006, falling in the third round to Benjamin Becker of Germany. He received an eight-minute ovation from the crowd and made a tearful retirement speech.

A kinder, more fulfilled Agassi has emerged since then. These days he devotes a lot of time and money to the Andre Agassi College Preparatory Academy, which he set up in Las Vegas in 2001 to give free tuition to at-risk and abused children in a rough neighbourhood. With his other charitable projects, he has been described as the most philanthropic athlete of his generation.

It is an amazing story. What a shame he had to go and spoil it.