The American is also seeking a record-equalling 24th Grand Slam title in her highly anticipated final against Canadian teenager Bianca Andreescu, the number 15 seed, after injuries affected her form in some tournaments this year.

Andreescu looks to cap 'crazy' year with the ultimate scalp

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The 37-year-old's long-time coach said it had been a winding road following the birth of her daughter in 2017 to the kind of peak performance that brought her U.S. Open success in the past.

"Her body transformed to become a mother," Mouratoglou said on Friday. "You don't come back to your previous body, which is the body of a professional top athlete, overnight. It takes time.

Patrick Mouratoglou is the coach of Serena Williams

Image credit: PA Sport

"So that was the first goal, to be completely in shape and able to perform at the highest level physically."

Williams claimed her last Grand Slam title at the Australian Open in 2017, before taking maternity leave.

She returned to competition at the French Open the following year, reaching the fourth round before withdrawing through injury, and reached the finals at Wimbledon and the U.S. Open.

Injuries have remained frustratingly in the picture, though, with a back problem forcing her to retire during the Rogers Cup final and withdraw from Cincinnati, after she again reached Wimbledon showpiece at the All England Club.

Williams also twisted her ankle during her quarter-final loss at the Australian Open.

Serena Williams goes in search of her record equalling 24th Grand Slam

Image credit: Getty Images

"She got injured several times, especially in the lower part of the body, which is very annoying because you can't do anything, basically," said Mouratoglou.

"You can't do sports and it delays a lot the moment when you'll be able to compete again."

But coming off the various injuries, the eighth-seeded Williams said throughout the U.S. Open that she had embraced a more intense and demanding training routine.

"I just feel like I actually had time to train," she said after her semi-final win over fifth-seed Elina Svitolina.

Bianca Andreescu faced Williams only last month

Image credit: Getty Images

"I just had a really tough year with injuries, mostly bad luck. I just needed to get injury-free."

Mouratoglou said she had done just that.

"Two weeks before Wimbledon, 10 days to be precise, (she) finally got rid of her knee problem and she was able to run without thinking about her knee," added Mouratoglou.

"So now it's several weeks in a row, so I think her fitness just went up and up."

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