Aston Villa captain Stiliyan Petrov is set to be sidelined for around two months due to a knee injury sustained in the 1-0 weekend defeat at Sunderland.
The 31-year-old Bulgaria international had to be replaced shortly before half-time of the Stadium of Light clash and may yet need to undergo surgery on the injury.
Manager Gerard Houllier confirmed: "Unfortunately I think we have lost Stiliyan Petrov for maybe at least two months.
"We will see if he needs an operation or not - we will know that by the middle of the week.
"It is a shame because he was getting up to a good level. It was a very unfortunate accident."
Meanwhile, another midfielder, Fabian Delph, hopes to be back in action in the New Year, following a lengthy recovery from a serious knee injury.
The 20-year-old damaged cruciate ligaments in his left knee in training in April, but is now positive about an eventual comeback.
He said: "Everything has been going really well and the physios, doctors and surgeons have been brilliant with me.
"I'm just looking forward to getting back on the pitch and playing again in the New Year."