Lisa Ryan, the Sheffield United Women's centre-half, has been ruled-out for the rest of the season with an anterior cruciate injury.
Ryan, signed from Arkansas based club Little Rock Rangers, is scheduled to undergo surgery after scans revealed the extent of the damage she suffered during September's win over Aston Villa.
Fellow defender Ellie Fletcher, on loan from Liverpool, is also scheduled to miss Sunday's visit to Millwall Lionesses after being diagnosed with a torn meniscus.
Doctors have confirmed the former England under-19 international, who has attended several under-21 training camps this term, will be absent for around three months.
"Unfortunately, Lisa will need to undergo an ACL operation, ruling her out until next season," manager Carla Ward, said. "We will be supporting her for the duration of her recovery."
"It's hugely disappointing for both girls because they had been working hard on the training ground to secure their places in the starting eleven and, when given the chance, they took their opportunities, putting in some great performances," she added.
Despite those set-backs, United travel to London knowing a win could see them climb to fifth in the FA Women's Championship, with only one game remaining before the winter break.
Ward's preparations have been boosted by the form of 16-year-old Izzy Ford, who scored on her full senior debut against Lewes last weekend, while Alethea Paul confirmed her return to fitness during the 3-2 victory.
Sophie Barker and Sophie Jones were also on target as United impressed at their new home, the Olympic Legacy Park in Attercliffe.