Doctors have told Luck, 29, that his fracture has failed to heal properly, despite having surgery at the end of last season.
Team doctor John Mayhew said Luck would now have a bone graft to repair the damage caused, putting his planned return back a few weeks.
“It’s a setback but that’s the way it goes. There’s no point worrying about it,” Luck told the club website.
“What’s most important to me is doing everything to help the boys get ready for the start of the season.
“I was already starting the season a bit late after the shoulder surgery I had before Christmas. Now it’ll just be a bit later.”
Luck had surgery on his left shoulder just before Christmas and Mayhew said Luck was recovering well from that operation.
Meanwhile, Mayhew said an operation yesterday to re-attach the right bicep tendon of prop Jacob Lillyman had been successful.