Serena Williams' obsession to match Margaret Court's all-time grand slam singles record has driven the American to crazy new training levels, according to her long-time coach and confidante.
Patrick Mouratoglou has guided Williams to nine major championships since linking with the former world No.1 in 2012, but says he has never seen her work as hard in pursuit of a 24th major at Wimbledon this week.
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Motherhood and a niggling knee injury had restricted Williams to nine matches since an Australian Open quarter-final loss to Karolina Pliskova in January.
But the 37-year-old now stands on the brink of history.
Williams will face unseeded Czech Barbora Strycova on Thursday for a place in the final and a third shot at Margaret Court's record 24 slams.
Losing last year's Wimbledon and US Open finals to Angelique Kerber and Naomi Osaka have only further fuelled Williams' desire.
While she often plays it down, Mouratoglou on Wednesday admitted equalling Court's benchmark tally - which has been untouchable for 46-years - is the very reason Williams returned to tennis after the birth of daughter Olympia in September, 2017, which also triggered a pulmonary embolism that left her bedridden for six weeks.
"Twenty-four will mean that she will equal the record of all time ... and that's why she came back to playing tennis after having a baby and so many medical complications," he told reporters at the All England Club.
"The effort she has put in, I have never seen something like this.
"You have no idea how much she worked, how hard she worked to come back to that level and she came back for that (record) so it will probably mean a lot if she makes it."
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After shedding some kilos and also playing "so much lighter" in spirit following her return to full health in recent weeks, Williams is a heavily favoured to beat Strycova for the fourth time in as many meetings.
"She is in a good place at the moment," Mouratoglou said.
"She is happy, has a house, her husband is here, her daughter is here and she is pain free.
"In the last match you could see that she has been able to raise her level when it was necessary, which is one of her trademarks and this is back.
"So everything is positive."
Victory over the 54th-ranked Strycova, who, at 33, is the oldest first-time grand slam semi-finalist in 50 years of open-era tennis, would vault Williams into an 11th Wimbledon final on Saturday.
The world No.10 would play either Romanian seventh seed Simona Halep or Ukrainian eighth seed Elina Svitolina, who clash in Thursday's other semi-final.