Manchester City have confirmed that Mary Fowler has suffered an anterior cruciate ligament injury. (More Football News)
Fowler suffered the injury during Sunday's FA Cup semi-final defeat to Manchester United.
The 22-year-old has been in excellent form for City this season, and leads the Women's Super League for goal contributions, with 13, along with Elisabeth Terland, Alessia Russo and team-mate Khadija Shaw.
However, the Australia international will now miss the remainder of City's campaign and likely much of the first half of next season.
A City statement read: "Mary will remain under the care of the club's medical team and start her rehabilitation.
"Everyone at City wishes Mary all the best on a full and speedy recovery."
Fowler has provided seven assists in the WSL this term, more than any other player.
On average, she has come up with a goal contribution every 86 minutes.
Fowler joins fellow City stars Lauren Hemp, Risa Shimizu and Alex Greenwood in suffering a long-term knee issue.
Star forwards Vivianne Miedema and Shaw are also out due to hamstring problems.
Nick Cushing's team are seven points behind third-place Man United, and are in real danger of missing out on Champions League qualification.
They host Everton in their next outing.
