Eddie Howe's side missed out on the chance to close in on the npower Championship play-off places when they lost 1-0 at Reading on Friday and the Clarets currently sit four points shy of the top six.
However, veteran defender Duff points to a run of nine wins in 15 league games - which began with an astonishing 3-2 comeback win to prevent a fifth consecutive loss at Hull in November - as evidence of Burnley's progress.
"I'm sure we would have taken this position when we were 2-0 down against Hull," he said. "In the last few months we've shown a little bit of consistency. We've looked a solid unit and looked like a decent team.
"Earlier in the season we looked a great team one week and were shipping goals the next. The consistency has coincided with us being a lot more solid as a team. We haven't conceded as many and we're still scoring goals.
"It's not something we really want to go on about and it's not just the back four - I think the whole team as a unit has looked a lot more solid and that's a foundation to build from. If we can keep people fit and keep the run going you never know where it might take us."