But the Newcastle winger has returned to full training after a serious foot injury threatened his career.
Irish Eyes Are Smiling For Toon Winger!
The 28-year-old last appeared for the Magpies at Portsmouth in April when he limped off with what seemed to be a minor knock.
The Republic of Ireland international has had two operations but is now on his way back to action.
Sam Allardyce: "It's great to see Damien back in training.
"He is just starting to join in with the players, and there will be a period of time when he gets used to training on a day-to-day basis.
"He'll have to get used to the physical contact first of all, and from there we'll take it into a reserve match.
"We hope we'll have him back to the sort of level we know he can play at as quickly as possible.
"We're looking forward to having him back in the first-team squad, because Damien is a player of undoubted class who can play a big part for us this season."
Duff has managed just 20 league appearances for the Magpies since his £5million transfer from Chelsea in July 2006.