Former Claret claims Leicester City are a stronger side than Burnley's Championship winners
and live on Freeview channel 276
Duff says a meeting with Leicester, who have won 10 of their 11 league games this term, is "probably the toughest game of the season".
"I think they will win the league," he said.
"I think they are better than Burnley last year, which probably tells you everything.
“We will have to suffer without the ball at times because they are a very good team, but what we don't want to do is just sit in a block of 10 men behind the ball and hope to survive for 95 minutes.
"I think we have proved in the last few weeks that we can play and that we can defend.
"We will have to be at our best, no doubt about it, but there's no apprehension. We will go out intent on trying to win the game.
"Teams have gone different ways about trying to beat them and they have worked it out every time because they have got good players.
"We will have to try and come up with something and impose us on them."
Duff made 342 appearances for the Clarets during a 12-year spell as a player, having previously represented Cheltenham Town.
The former centre-back began his coaching career with Burnley’s academy before taking on the manager’s role at Cheltenham.
Duff made the move to Swansea this summer after a year with Barnsley.