Meet Alex, the taxi driver who becomes a Grand Slam-winning coach of Sofia Kenin

Russian-born Alex Kenin, an unassuming, grey-haired man with a receding hairline, introduced Sofia to tennis, brought her up around the game and pushed her to achieve the extraordinary -- crowned by her victory at the Australian Open on Saturday.

Sofia said her "crazy smart" father had no prior experience of the game, but simply picked it up by observing those around him.

"He's seen how all the other coaches have been coaching their players, but he knows everything," Sofia said, after stunning Garbine Muguruza in her first Grand Slam final. "He knows what he's talking about, he really knows it and he comes up with the right plans, the right strategies."

Also Read: The American Dream: Sofia Kenin becomes youngest woman to win Grand Slam at Australian Open

If Sofia's achievement is remarkable, it owes a great deal to her father, who was ever-present courtside during her increasingly impressive run through the Melbourne women's draw.

Teenage prodigy Coco Gauff, world number one Ashleigh Barty and, in the final, two-time Major-winner Muguruza all fell victim to tough-as-boots Sofia, who was following strategies drawn up by her wily father.

He joins a long list of tennis dads who have produced champions, including Richard Williams, father of Venus and Serena, Mike Agassi (Andre) and Yuri Sharapova (Maria). But unlike some other fathers, whose influence has been resented or even negative, Alex and Sofia, 21, remain close and affectionate.

"I really have him to thank. We've been dreaming about this -- it's a dream come true for us," Sofia said. "He's told me a lot of positive things. He knows exactly what he's talking about.

"Even though I don't like to admit it sometimes, to tell him he's right. Yeah, he really works hard. Just thank you to him. We can share this forever."

Alex Kenin arrived in New York from what was then the Soviet Union in 1987 with his wife, Lena, and a few hundred dollars in his pocket, searching for the "American Dream".

He drove a taxi by night and went to English and computer school during the day, a period he describes as "very, very tough". "I had to work at night, go to school in the morning. Driving in New York, speaking English on the (taxi) radio. I had no idea what they were saying," he said.

"But it's amazing the things you do to survive. (Sofia) knows about that and I think it made her tough."

During Saturday's final, Alex could barely watch as Sofia closed on the win, and he filmed her winner's speech -- which was beamed live worldwide -- on his mobile phone. "He was so happy. I was so happy. We shared this together. He was like, 'What just happened?'" Sofia said. "I'm also just on cloud nine."