Maria Sharapova admits that her memoir, “Unstoppable: My Life So Far,” was scheduled as part of her 2016 retirement tour, ending “at the US Open … just as this book hit the stores.” But then she tested positive for a banned substance and received a two-year suspension, reduced on appeal to 15 months. So she turned to Plan B – a comeback in the spring of 2017, leading up to the year’s last Grand Slam at Flushing Meadows, capped by publication of the book and her triumphant return to the top of the game.

Instead, she encountered bitter resentment from other players and harrumphing from the press. She lost at her first tournament in Germany, withdrew injured from the Italian Open, was refused entry at the French Open and Wimbledon, and retired from a tournament in California with yet another injury. This prompted snarky online comments that she couldn’t win without chemical help. But the U.S. Open welcomed her with a wild card, and she reached the fourth round before losing and coming in for more criticism for receiving preferential court assignments.

One can only marvel at the fall of the five-time Grand Slam champion, the glamorous spokeswoman for luxury products and the richest female athlete in the world. To convey this kind of calamity would require a Greek tragedy, not an as-told-to autobiography. But “Unstoppable” does offer clues to why Sharapova finds herself with few friends on the pro tour.

Sharapova was born to a monomaniacal father who taught himself tennis, then imposed it on his child. These events transpired in Russia after the nuclear meltdown at Chernobyl and the breakup of the Soviet Union, adding to the implausibility of the tale, which reads like a Horatio Alger story on steroids (Sharapova’s drug ban, by the way, was for meldonium, a heart medicine suspected of being a performance enhancer, not for steroids). Leaving his wife in Russia, Yuri Sharapov bundled his daughter, age 7, off to Florida with $700 in his pocket and a conviction that they could crash an elite tennis academy and catapult the family into the misty American Dream. For years they survived on the kindness of strangers, Yuri’s native cunning, Maria’s talent and no small amount of luck. If Yuri was constructed of steel, Maria was forged out of titanium. She jokes that she willed herself to grow to be 6 foot 2, and although of limited speed and mobility, she never lacked “determination, tenacity. I do not quit. Knock me down ten times, I get up after the eleventh and shove the ball right back at you.” And every stroke she hit was punctuated by a banshee shriek.

At the start, she competed with an adult racket cut down to child size and wore Anna Kournikova’s castoff clothing. She and Yuri slept in the same bed at the home of a Russian emigre who sometimes served as a surrogate mother and sometimes threatened to evict them. Maria learned English from watching TV and received almost no formal education. She didn’t see her mother for years but professes to have no regrets about her childhood. As she says, how could she miss something she never had? If welfare authorities in Florida had known how she was living, they would probably have taken her into foster care. The same might be said of many kids at tennis academies – places Andre Agassi characterized as “Lord of the Flies with forehands.”

An outlier from the start, Sharapova viewed her estrangement as an advantage. She showed “no emotion. No fear. Like ice. I was not friends with the other girls, because that would make me softer, easier to beat.”

She worked with a rogue’s gallery of coaches, some positive influences, some exploitative, all ultimately discarded like sweaty socks on the locker room floor. When she dropped her father as coach, she sent him “an email because I felt that was the best way I could express my feelings.” The coach she liked best was Robert Lansdorp who called her, age 11, a “broad” and told her, “Get your ass out on the court.”

Tough love was all she understood and, later on, all she had to offer. Her first serious romantic relationship with an NBA player foundered because “my success, my fame, and my wealth were evidently becoming a struggle for him.” From this she concluded, “If you are on the tour, then you have to be the man, no matter your gender.”

Later she fell in love with a Bulgarian tennis player, Grigor Dimitrov, but it hit her that they had no future when she sat watching him play a tournament where she had lost. “I was supposed to be focused, getting prepared for my own matches, my own triumphs and defeats, on the largest stage of my career.” She had no interest in cheering him on. She was the show.

When she lost, as she often did, to Serena Williams – their “legendary rivalry” stands at 19-2 in Williams’s favor – she sought “retail therapy. When you feel you need to see a psychologist, go out and buy a pair of shoes instead. If they’re really great shoes, all your worries will evaporate.”

The memoir ends where it began, with Sharapova’s bravado about never quitting “until they take down the nets. Until they burn my rackets.” I’d recommend that the author of “Unstoppable” pause, reflect a bit deeper, and cut herself and everyone else more slack.

Mewshaw is the author of 21 books, most recently “Ad In Ad Out,” a collection of essays on tennis.