By Sudipto Ganguly

MELBOURNE (Reuters) - Sofia Kenin shed a few tears and needed to find a way to keep her emotions in check during an epic final against Garbine Muguruza, but soon after lifting her first Grand Slam title the American had to rush to calm someone else down - her mother.

Kenin counter-punched her way back from a set down against Muguruza to win her first major at the Australian Open with a 4-6 6-2 6-2 win on Saturday.

The 21-year-old was almost reduced to tears in the third set and even threw her racquet away in frustration at some of her shots.

"I felt that in the third set, I felt like I was getting closer to the title, something that I really want," she said after toasting her win with a glass of champagne

"I knew I needed to somehow try and relax, just try to calm down."

Eventually she found a way to do that, as twice Grand Slam champion Muguruza wilted in the latter stages.

But Kenin still had one more worry: her mother, who gets so nervous she finds it hard to watch her daughter play.

"I called her right after the match just to tell her that everything's fine, I won, she can just relax now," she said, before bursting into laughter.

"She's been really stressed at home, very superstitious. She's just really happy. I told her I'm not going to be able to talk to you for hours, but at least you know that I won. I'm coming home, you can give me the biggest hug of your life.

"My mom cannot watch me. I can see she's still nervous. She doesn't like watching. It's fine."

Kenin, who had to dig herself out of trouble on numerous occasions during the match, said she considered the fifth game of the last set to be the turning point, when she painted the sidelines with three scorching winners and produced an ace to hold her serve for 3-2 from 0-40 down.

"I can remember that game very well, yes. That's the game I feel like changed things," she said, adding that next on her agenda was a trip to the Cartier store in Melbourne to buy herself a ring and nail bracelet.

"I had to play some best tennis. I did. After that, I was on fire. I was ready to take the beautiful trophy."

Kenin will become the world number seven when the WTA rankings are released on Monday which will move her past idol Serena Williams as America's top player.

"It hasn't sunk in yet. Everything is just still a blur for me. I just can't believe what happened," said the Moscow-born Kenin, whose parents are Russian immigrants. "It's just great. I feel like I'm doing some great things for American tennis. It's such an honor.

"I've watched Serena. I've been following her, all the slams she's been winning. It's a special feeling just to be ahead of her. I'm just super excited. I can't wait to compete, be on the same team with her in Fed Cup."

(Reporting by Sudipto Ganguly; Editing by Hugh Lawson)