Jim Mallinder is hoping the Saints medical staff can help solve his second row crisis this week.
Mallinder was without all four of his first-team locks on Saturday as his side fell to a 20-7 Aviva Premiership defeat at Sale Sharks.
Courtney Lawes has been nursing an ankle injury, Christian Day a back problem and James Craig has only recently returned to training.
Samu Manoa, who has predominantly been used at No.8 this season but can play in the second row, has been on compassionate leave.
But Manoa returned to Franklin’s Gardens today and Mallinder is desperately hoping the other three missing men will be ready to face Ospreys in the Champions Cup on Sunday.
“I’ll be putting quite a lot of pressure on our medics over the next few days to make sure they’re all back,” said the director of rugby.
“Samu’s been in America and has returned, and we’re quite positive that the other three will be fit for this week.
“James Craig has been very close for a long time. He’s running now and we’re hoping that in the next week or two he will be returning.”