Central defender Steven Taylor could be out for the first three months of the new season.
The 24-year-old has undergone surgery after dislocating his left shoulder in a pre-season friendly at Carlisle on July 17.
NUFC statement: "After further assessment on the injury over the past week, the medical bulletin is that it will be a three-month period of rehabilitation."
The latest setback happened on the former England Under-21 captain's first appearance since suffering a knee injury in January.


