Josh Jones is set to miss Friday’s clash with Huddersfield after suffering concussion in the 41-24 defeat against Warrington at the Magic Weekend.
Man-mountain prop Alex Walmsley and full-back Jonny Lomax are also set for short spells on the sidelines with hamstring and knee injuries, respectively.
Young centre Mark Percival is close to a return to first-team action, but may not be ready for this Friday.
Saints coach Nathan Brown said: “With the new rules on concussion Josh Jones is ineligible for this week. Hopefully he’ll only need a week’s rest.
“Alex Walmsley and Jonny Lomax will both be out for a short period. Neither of their injuries are disastrous though - they’re just short-term things.”
Brown has also challenged his players to “learn the lessons” from the recent Wigan and Warrington defeats.
He added: “Huddersfield will be at full strength and have got one of the best rosters in the competition. It will be a good challenge for us to try and rebound off a performance we weren’t so happy with.
“We want the boys to compete hard. It’s the performance level that’s the most important thing - not just the result. We seem to have had a positive week in training, but the proof is in the action.”