There were murmurings of discontent from the terraces as Burnley went down to a lacklustre 1-0 defeat against Hull at Turf Moor on Monday, an eighth winless game in their last nine.
Meanwhile, the lowest FA Cup quarter-final attendance on records stretching back to 1970 demonstrated the widespread disillusion at Rovers before a ball was kicked in Wednesday night's loss to Millwall.
But Burnley defender Duff believes the bitter rivals will be greeted by a cauldron of noise befitting the occasion at Ewood Park.
"We'll have three or four thousand fans and they'll be making a lot of noise," he said. "It's not a normal game on Sunday.
"Whether they've been getting a bit of stick at home or not, it'll be full with their fans and they'll all be behind them. We'll have an end and they'll all be behind us.
"It's a good game to look forward to, especially in the middle of this run. Form goes out of the window in derbies and hopefully that's the case."
Duff jokingly played up to derby hostilities when asked if he had any friends in the Blackburn side.
"I don't think so, no," he added. If I knew them I'd kick them anyway.
"Normally the more you know them the more you kick them."