Despite this setback, Millwall are hoping that Chadwick will return to The Den to complete his loan spell.
"We were expecting Nick to have this operation sometime during the month, and it has happened a little sooner than we anticipated," explained assistant boss, Ray Wilkins. "Once he's recovered, which should be in around 25 to 30 days, we're hoping that David Moyes will allow him to return to us to complete his loan spell."
Should Chadwick to return to Millwall, his loan spell will recommence where it left off as his current loan spell can last up to 93 days under current FA rules.