The winger called time on his Republic of Ireland career in August after winning 100 caps for his country.
Jol is now grateful that the 33-year-old won't be able to pick up injuries while away on international duty.
"Of course, there's always a risk of an injury when you play these games," the Dutchman told the Fulham Chronicle.
"I think he's got to 100 games and he decided to call it a day, so I won't say I'm happy he did that but it's certainly got a few advantages."
Duff scored eight goals during his 14-year spell in the Ireland side.