Jonny Lomax could be facing another lengthy spell on the sidelines.
Saints coach Keiron Cunningham told a press conference on Monday Lomax has suffered a injury to the same knee he damaged last year.
But the full extent of the injury is not yet known and Saints are waiting the resulty of a second scan.
The luckless full-back, who missed much of last season after snapping his cruciate ligaments, is still waiting for news on his latest injury blow.
Lomax, 24, fought back from the injury he suffered against Catalans Dragons last year to make a strong start to this season.
Meanwhile, Mark Percival, who also suffered a knee injury in the same game, is set to be out for six weeks after damaging his medial ligaments.