Maria Sharapova says being a teenager with “a few hundred dollars” and “no sense of the future” was the toughest period of her career – not losing in the US Open last 16.

The five-time Grand Slam champion has not gone past the quarter-finals in her five major appearances since returning from a doping ban in 2017.

The Russian, 31, lost to Spain’s Carla Suarez Navarro in New York on Monday.

“I think I’ve done plenty in my career,” said Sharapova.

“[I’ve] established a lot for myself personally, professionally.”

Sharapova became a household name when she won the 2004 Wimbledon title as a 17-year-old, going on to claim a career Grand Slam with victories at the Australian Open, French Open and US Open over the next 10 years.

The former world number one slid down the rankings after being given a 15-month doping ban for using meldonium.

She tested positive for the banned substance, which is used to control heart disease-related conditions, at the 2016 Australian Open, but has always denied cheating.

Since returning to Grand Slam action at last year’s US Open, she has climbed to 22nd in the rankings and reached one quarter-final at Roland Garros in June.

Asked if Monday’s defeat represented the most challenging period of her career, Sharapova – who left Russia for the United States with her father as a seven-year-old – said: “What’s challenging is when you’re a teenager and you have a few hundred dollars and you’ve got no sense of the future.

“You don’t know where you’re going to end up. You just have a dream.

“That’s a lot tougher than being 31 years old and having the opportunity to do whatever I want in my life.”

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‘I wouldn’t be here if I didn’t think I could win again’

After losing to 30th seed Suarez Navarro 6-4 6-3, Sharapova added she would not still be playing if she did not believe she could challenge for Grand Slam titles again.

“If you don’t have belief, it’s your choice to not continue that,” she said.

“If I didn’t have the belief to keep doing this and to keep having the motivation and the grind of doing this every day in order to get myself in these positions, I don’t think I would be here.

“The belief is not something that I’m eager to show everybody else.

“The belief matters most when it’s internal and when you have a passion for something.”

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Roger Federer has been knocked out of the US Open in the fourth round by world number 55 John Millman.

The 37-year-old Swiss had prioritised winning a sixth title at Flushing Meadows but was beaten 3-6 7-5 7-6 (9-7) 7-6 (7-3) in three hours 38 minutes.

It is the first time Federer has lost to a player ranked outside of the top 50 at the US Open.

Australian Millman will play two-time champion Novak Djokovic in his first Grand Slam quarter-final on Wednesday,

Second seed Federer, bidding for a record-extending 21st Grand Slam, missed set points in the second and third sets before capitulating in the fourth-set tie-break.

Millman, 29, had never beaten a top-10 player before but suddenly found himself with five match points against arguably the greatest male player of all-time.

After Federer rallied to save two of the them, Millman completed victory at almost 01:00 local time in New York when the out-of-sorts Swiss lumped a forehand long.

It was Federer’s first defeat in 41 matches at the US Open against a player ranked outside the top 50.

Warning signs were clear for Federer

After not dropping a set in his opening three matches, Federer looked on his way to another controlled victory when he eased the opener in 33 minutes.

However, the warning signs were clear from the start of the second set.

Federer’s reliable serve has been the bedrock of his game over the years but an uncharacteristically erratic display allowed Millman to fight back and earn a memorable win.

The world number two produced a contender for one of the ugliest service games of his career, unable to find his timing as he landed just six of his 24 first serves in a 14-minute second game.

He somehow managed to hold after fighting off seven break points, before breaking Millman’s serve himself to lead 3-2.

But, with his first serve percentage down at 31%, Federer still looked uncomfortable.

He blew two set points when serving at 5-4 and a double fault at break point gifted Millman the game and the Australian broke again as he won four games in a row to level the match.

Willed on by a supportive crowd on Arthur Ashe Stadium, Federer managed to steady his service game in a tight third set and missed a set point in the tie-breaker when Millman hit an outrageous 100mph second serve down the middle.

The Australian wasted one of his own with a long return as Federer battled to stay in the set, only to take his second chance and leave Federer facing an uphill task.

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Britain’s Jamie Murray and his Brazilian partner Bruno Soares reached the men’s doubles quarter-finals at the US Open without dropping a set in three matches.

The fourth seeds, who won the title in 2016, beat Dutchmen Robin Haase and Matwe Middelkoop 7-6 (7-4) 6-4.

They face unseeded Radu Albot of Moldova and Tunisia’s Malek Jaziri in the last eight.

Murray is back on court later in the day for a mixed doubles quarter-final.

He and American partner Bethanie Mattek Sands take on Nadiia Kichenok and Wesley Koolhof.

Fellow Briton Dom Inglot and Croatian partner Franko Skugor saw their run in the competition ended by American third seeds Jack Sock and Mike Bryan, who won 6-2 6-4.

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Last year’s runner-up Madison Keys is through to the quarter-finals of the US Open after she defeated 29th seed Dominika Cibulkova 6-1 6-3.

American 14th seed Keys broke twice in the first set and again on Cibulkova’s first game in the second.

She dropped serve shortly afterwards but broke back twice to win in one hour and 16 minutes on Arthur Ashe.

Keys will face the winner in the match between Maria Sharapova and Carla Suarez Navarro in the quarter-final.

She said: “I am glad I got the win and can come out here again for another match. It’s always easier to be more energised when the person on the other side of the net is more energised than you can possibly be.

“She’s a good player and has done a lot in her career. It was about having to focus on first serves and waiting for the right ball. I had to move my feet and used the crowd in those tight moments.”

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