Luther Burrell looks set to miss Saints' trip to Bath after being unable to train due to a shoulder injury sustained last Saturday.
Christian Day also appears likely to be unavailable due to concussion, while Alex Waller remains sidelined as he continues to recover from a broken arm.
But interim head coach Alan Dickens says Tom Wood's groin injury is not as serious as first feared and believes James Craig is not too far away from recovering from a knee problem.
Saints travel to Bath in the Anglo-Welsh Cup semi-finals on Friday night.
And it looks likely that they will be without Day, Burrell, Wood, Waller and Craig as well as Six Nations stars Dylan Hartley, Courtney Lawes and George North.
Day, Burrell and Wood were all forced off during last weekend's 34-25 Aviva Premiership defeat to Sale Sharks.
And Dickens said: "Christian Day, as always with head injuries, is going through the return-to-play protocol so we're keeping a close eye on him.
"Luther Burrell came off with a shoulder injury so he's not trained during the early part of the week. I'm not sure how long he will be out for.
"Tom Wood's injury is not as serious as we first thought so it's positive news on him.
"Alex Waller is the same as last week in terms of being another week or two away.
"James Craig is not too far off so it's good news for him."