The Reds boss gave his thoughts after a frantic affair in Milton Keynes on Saturday afternoon.
James Norwood's opener on the half-hour mark preceded a hectic second half at Stadium MK, with the hosts scoring four in 21 minutes to garner a three-goal lead.
However, the Reds turned it around, with Norwood and Max Watters both netting braces to confirm a level ending to the match.
Despite mounting a second-half comeback, Duff was discontented with his side's showing on the afternoon.
"I'm disappointed with the performance," he expressed. "Lots of it, I wasn't particularly happy with if I'm being brutally honest. We'll pick the bones out of it, like we always do.
"Too many basic, elementary errors, intensity, duels, conceding goals from set plays. All of a sudden, the fourth goal goes in and we kick into who we are. We run forward, get a bit of energy into the team and we did what we did. It's not the result, it's more of the basic elements of the game that we didn't do."
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