The scrum-half has been ruled out for three to four months after damaging ankle ligaments.
That injury is almost certain to keep him out of Wales' Six Nations clashes with England, Scotland and France in February.
But there is now increasing concern among the Ospreys management that Phillips, who started all three Tests for the Lions against the Springboks during the summer, may be out for even longer.
And that would leave Wales' first-choice number nine as a major doubt to be fit for the final ties with Ireland and Italy in March.
"Mike's return is off the radar and we're looking at three to four months. I don't know if he'll see any of the Six Nations," admitted Ospreys coach Sean Holley.
"My focus is on this Saturday and then the European ties. But I know he's not going to be available at any point in 2009.
"We get updates every day but with Mike it has been a very quick one. We have to work like that, we have to have priorities."
Phillips, 27, suffered the injury when he limped off in the Welsh region's Heineken Cup win over Clermont Auvergne in October.
And there was further bad news for Wales coach Warren Gatland after fellow 2009 Lion Matthew Rees was ruled out for three months.
Scarlets hooker Rees, who started both the second and third Tests against the Boks with Britain and Ireland's elite, will see a specialist on Friday to establish whether he needs surgery on a torn groin muscle.
"Scans of Matthew's injury have been done and from the initial reports we have had, I would not expect him to be available for at least the next 12 weeks," said Scarlets doctor Mark Ridgewell.