Saints have been unable to put an initial timescale on how long Matty Smith will be marked absent.
The scrum-half, who missed the earlier part of the season due to a broken leg which he suffered in a pre-season friendly against Widnes Vikings, only lasted seven minutes in a 24-22 defeat at Leeds on Thursday, picking up a horrific injury.
He appeared to have part of his eyelid ripped off in a collision during a tackle.
Head coach Justin Holbrook said: “Unfortunately, the injury is a bit on-going and not clear cut at this moment in time.
“He had surgery on Friday and more today which hopefully will give us a clearer picture of the problem.”
Holbrook added: “At the present time it is a work in progress, but all that really matters is that he will be OK at the end of the day.”