The 32-year-old suffered a calf injury 20 minutes into the new season and was out for a month before being dropped to the bench for the last five matches. However, he made his return in the 1-1 draw with Millwall on Saturday, coming on as a ninth-minute substitute to fill the void left by Carlisle's dismissal.
Now, following the Clarets' unsuccessful appeal against Carlisle's red card, Duff hopes to be at the front of the queue to start his first game since the opening day when Brian Laws' side face Sheffield United on October 16.
He told the club's official website: "This is what you wait for. It's disappointing when it's someone else's misfortune but that's how it works. I've had an opportunity now.
"Clarkey has taken his opportunity well when I got injured and this is what a squad and competition are all about.
"Clarkey is suspended for three games, so hopefully I will get in the team and kick on from there. I thought I did okay (against Millwall) and hopefully I will get a chance in the next game."