Newcastle United midfielder Hatem Ben Arfa could be ruled out for the rest of the season if he has to undergo surgery on his hamstring.
The France winger only returned from a three-month absence through injury in last week's Europa League last-16 first leg at Anzhi Makhachkala, having been out since suffering the injury in the 2-1 defeat Fulham back in early December.
However, he has not played in either of the two games since that 0-0 draw, and has been told an operation may be the only solution.
Manager Alan Pardew said: "Looking at him, I think he's going to need an operation on his hamstring, and it will probably leave him missing for the rest of the year, I think. We have had to absorb that in all the good news that we have had."
Another enforced lay-off would represent another setback for Ben Arfa, who missed all but four games of his first season at the club with a double leg fracture, and Pardew said it now appears that the 26-year-old will have to write off another campaign and focus on a summer return.
"That's the priority for him now because he's been a huge miss for us," Pardew said. "He gives us that X-factor. In a game like last night's where he could open the door for us, we haven't got that luxury.
"Unfortunately for Hatem, that's the news that he didn't want to hear. But as far as we are concerned, the team has responded well in his absence and hopefully, we do that until the end of the year."
There was a fitness boost for Pardew, however, as midfielder Yohan Cabaye could recover from his groin injury in time for Sunday's Premier League trip to Wigan.