Manchester United boss David Moyes has revealed that Nani is poised to be out of action for "quite a while" after the winger sustained further damage to a hamstring injury.
The Portugal international has been absent from United's first team since early December, with the initial prognosis thought to be a number of weeks.
However, Moyes has confirmed that the 27-year-old has suffered a setback in his return to fitness, but reveals that full-back Rafael da Silva is among those closing in on a return to action.
He told the club's official website: "Nani has got a hamstring injury which is probably going to keep him out for quite a while.
"It's a serious hamstring injury that he picked up in training. I don't think Rafa is too far away, though, as his injury isn't too serious. Hopefully, we're beginning to get one or two back."
The Red Devils host Swansea City at Old Trafford in a third-round FA Cup clash on Sunday afternoon.