"I'd always put 12 months [out of action] on an ACL [injury], and then you can work back from that," United manager Marc Skinner said on Tuesday.

"We should prepare for that, that's sensible."

George joined United from Everton in the summer and has made four appearances for the Red Devils.

She is the latest high-profile women's footballer to be sidelined with an ACL injury.

In September, United midfielder Emma Watson and Scotland team-mate Caroline Weir ruptured their anterior cruciate ligaments while on international duty.

Arsenal's Leah Williamson and Vivianne Miedema have also sustained ACL injuries in the past few months, while Gunners striker Beth Mead returned to action after 11 months out with a serious knee injury on Sunday.

Last month, Birmingham City's Siobhan Wilson said players were "scared" and "worried" by the rise in ACL injuries in women's football.

"It's an horrific injury for a footballer because it's just a period of time out," added Skinner.

"It's obviously devastating news for her. I've spoken to Gabby, she's in good spirits."

Skinner confirmed George will have surgery on her knee in the next few days.