Manchester City winger Martin Petrov looks almost certain to need surgery on his injured knee and will face up to four months on the sidelines if the operation goes ahead.
The Bulgarian picked up a ligament injury on international duty and despite City's best efforts the ailment has failed to respond to a tailored rehabilitation programme.
The former Atletico Madrid star returned to Spain to see a specialist and will remain in the country to undergo surgery, if required.
City manager Mark Hughes said: "Martin is going to see a surgeon ... he will probably stay and have an operation.
"If that is the case he will probably be out for three to four months. That would be a blow for us as he gives us more options.
"Unfortunately it is a frustration for us as it happened on international duty. That makes it a bit more difficult to take.
"Martin had a good pre-season and last year he was one of our outstanding performers. But at the moment it looks as though he will have to go in for an operation."
The 29-year-old's absence has coincided with an alarming dip in City's form, so much so that murmurs are beginning to be heard regarding Hughes' future with the club.
Meanwhile, captain Richard Dunne is doubtful for the UEFA Cup match against FC Twente on Thursday at Eastlands.
Dunne has fluid on the knee following the defeat by Bolton Wanderers on Sunday and his fitness will be monitored in the hours leading up to the game.
Benjani (thigh), Darius Vassell (knee) and Michael Ball (ankle) could all come into contention after injury problems.