Alan Gaffney confirmed Luther Burrell suffered a shoulder injury during Saints' defeat to Sale - and says the centre 'was in a fair bit of pain'.
Burrell only recently returned from a calf injury, which he suffered in the January 6 win against Gloucester.
But after starting three successive games, he could now be set for another spell on the sidelines after being forced off just three minutes into the second half on Saturday.
Burrell was replaced by Stephen Myler, with Piers Francis switching to centre.
Saints also lost skipper Christian Day, who was knocked unconscious, and Tom Wood to injury early in the game, with both forwards exiting the pitch inside the opening 10 minutes.
"Luther doesn't look too good," Gaffney said. "His arm was in a sling and he was in a fair bit of pain. It was a shoulder injury.
"Daisy didn't look too bad to me at all and I think Tom Wood got a groin injury.
"We'll just have to examine it and I don't quite know exactly where they sit."
Heinrich Brüssow was forced to leave the field during the second half, but the South African flanker passed a head injury assessment and returned to the action.
"It's great to see someone like Heinz Brüssow, who has probably got a different attitude to a lot of others," Gaffney said. "He can't wait to get back on the pitch."