Chelsea’s Australian striker Sam Kerr is undergoing surgery on Thursday to repair the anterior cruciate ligament she injured while training in Morocco.
Kerr, 30, who has scored 99 goals in 128 matches since joining Chelsea in 2019, will miss the rest of the season.
“I’m gutted for her. I’m gutted for the team. The recovery and the rehab begins today,” said Chelsea boss Emma Hayes.
“These things happen in football and she knows that. The important thing is we’re here to support her.”
The Blues lead the Women’s Super League by three points from Manchester City and return to action following the winter break on Sunday when they take on West Ham in the Women’s FA Cup.
During her time at Chelsea, Kerr has won four WSL titles, three FA Cups, two Women’s League Cups and the Women’s Community Shield.
Kerr has already struggled with injury this season, missing part of last summer’s World Cup with a calf injury and she has just recovered from a foot injury which kept her out of her country’s friendly internationals against Canada last month.
This latest one will see her miss Australia’s Olympic qualifiers against Uzbekistan next month and she would also miss this summer’s Paris Games, if they qualify.
She joins a long list of women’s players who have suffered similar injuries with England duo Beth Mead and Leah Williamson, Vivianne Miedema of the Netherlands and Canada’s Janine Beckie all missing the World Cup.
Hayes, who leaves the Blues at the end of the season to become the US women’s team head coach, added: “I know Sam would expect me to say nothing less than our focus has got to be on the players that are fit.
“We have a quality squad and it’s a good challenge for me as a coach to find those solutions. I trust in the squad that we have.”
Hayes also said Chelsea captain Millie Bright is continuing her rehabilitation after injuring a knee in November but still does not know when the England defender will return.
Hayes wants ‘many more years’ of Kirby at Chelsea
The return to fitness of midfielder Fran Kirby has been a boost for Chelsea this season after her eight-month absence through injury last year.
But the England playmaker has just six months remaining on her Chelsea contract and told BBC Sport earlier this month there have been “no conversations” between her and the club about extending her stay in London.
Kirby said she still has more to give and manager Hayes agreed but pointed out questions over Kirby’s future at Chelsea are for the club and not her.
“I think she’s been working her way back into staying fresh and available for the team. I think there’s still a gap to close for her,” Hayes said.
“But with regards to her future, it doesn’t have anything to do with me. I think it’s important to recognise that the club will make the decisions they make going forward. The season didn’t start until October. There’s still plenty of time for those things to happen.
“I think Fran is, of course, committed and focused on contributing to Chelsea and I hope that we get to see many more years of her in a Chelsea shirt.”