Jim Mallinder confirmed Piers Francis picked up an ankle injury during Saints' defeat to Wasps at Franklin's Gardens on Saturday.
Francis was helped from the field during the second half as his side suffered a 38-22 loss.
The 27-year-old, who moved to Northampton from Super Rugby side the Blues during the summer, had kicked well, registering four penalties.
But his participation in England's autumn internationals could now be in doubt.
"He's done something to his ankle, we're not exactly sure what," Saints boss Mallinder said.
"He said he did it early in the game and then got another knock on it with a few minutes to go.
"Hopefully it's not too bad.
"If there's any doubt, we'll get him in for a scan to see the extent of it."