Ilias was forced to hobble off the field in the dying stages of the Rabbitohs' NSW Cup clash with the Warriors after being tackled by Freddy Lussick.
The Warriors hooker attacked Ilias's right leg at Accor Stadium on Saturday as the Rabbitohs playmaker tried to kick the ball away, letting out an audible scream of agony.
The tackle - which led to Lussick being sent off - sparked an all-in brawl.
Earlier in the match Ilias had scored a try in an impressive display as Souths won 26-20.
But he was forced to limp off the field with help from the club's medical staff and was later seen on crutches walking up the tunnel alongside NRL head coach Jason Demetriou.
"I think they're talking about a tibia fracture, so he'll obviously have to get scans and we'll know more about it," Demetriou said.
"It was pretty sad to see.
"I didn't see the tackle. I was in the change rooms and I'd heard that Lachie had hurt himself, so I came out to make sure and to see that he's all right first and foremost.
"From what I heard, it was ordinary, but I didn't see it. I'm sure the match review committee will look at it in NSW Cup."
Ilias's absence adds to a growing list of unavailable players that already includes Jai Arrow, Alex Johnston, Tyrone Munro and Campbell Graham.
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