Jones set to miss Madrid encounter
No reason was given by the Old Trafford outfit for the absences.
However, England Under-21 coach Stuart Pearce has confirmed Jones is suffering from shingles.
"Jones picked up shingles and there's not a lot we can do about it," said Pearce in quotes carried by several national newspapers.
"It's a shame because it makes us stronger when Phil's here, that's for sure. But it gives someone else a chance."
A similar virus to chicken-pox, shingles is relatively common and the symptoms last for at least a fortnight.
So, depending upon the severity, it is difficult to see Jones recovering in time to make the trip to Madrid for next Wednesday's game.
It would be a blow to Sir Alex Ferguson too as the youngster recently excelled in a central midfield role against Tottenham and United might have been looking for Jones to carry out the same duties again as they look to get a positive result to take back to Old Trafford for the decider on March 5.