Fia damaged his knee in the team's gutsy 20-17 win over the Chiefs in Hamilton on Friday night.
He walked gingerly off the field and his knee was immediately put in a brace.
The Highlanders are hoping to get a scan on the knee today but coach Jamie Joseph said it was not looking good.
''We are looking at perhaps three months or maybe even longer. We'll know much more once we get the scan done. But it was tough for him. He was pushed over and twisted his knee,'' he said.
The side had been down to the bare bones in the propping department with Bay of Plenty duo Pingi Tala'apitaga and Kane Hames both off the field.
Hames is suspended and will not be sighted again until next month after picking up a five-match ban for striking in the match against the Crusaders on February 21.
The Highlanders can bring in another prop and would wait until the full extent of Fia's injury before deciding on a replacement.
Joseph said Hames' suspension would not impact on bringing another player in.
But the suspension obviously still rankles Joseph.
''In that game against the Crusaders there were two punches and one guy got one week and the other one got five. Then the other day some guy is messing around with cocaine and he got six weeks.''
Joseph declined further comment but the Highlanders will feel they have been on the rough end of the judiciary.
The system appears to have few rights of appeal and Hames has been treated harshly.
Fia is a specialist tighthead prop and they do not appear to be growing on trees in New Zealand rugby.
Southland prop JP Koen filled in for the Highlanders last year while Otago options such as Hisa Sasagi or Donald Brighouse appear to be too green.
Joseph said loose forward Dan Pryor picked up a concussion in the win on Friday night and was unwell on Saturday.
Whether he was available for the match against the Waratahs would be decided later in the week.
A few other players were a bit bruised and battered but the side had an extra day to recover before Saturday.
The Highlanders have had something of a horror draw, having to play the most successful Super rugby side, the Crusaders, first up, before meeting the three teams who have combined to win the past four titles.
After that is the in-form Hurricanes, while table-toppers the Stormers finish off a tough opening six games.
''It is horrible draw really. But we've got to keep on accumulating points and playing as well as we can.''
As of last night, captain and fullback Ben Smith and his wife, Katie, were still waiting for the birth of their first child.