The gaffer spoke to iFollow Barnsley following our 2-1 victory at Peterborough United, a result that saw us record our fourth consecutive league win.
A Luca Connell strike just after ten minutes played was cancelled out by a Jack Tayor header, before Adam Phillips continued his good form in front of goal and got what turned out to be the winning strike just after the hour mark.
Duff was full of praise for his team in how they applied themselves under the lights on Friday night, especially against a side who were fourth in the division prior to kick-off.
"Yeah, delighted," began the 44-year-old. "I thought we showed all sides of the game. I thought we passed the ball really, really well - particularly in the first half an hour. We showed some moments of quality.
"At the end of the game, I didn't feel as if we were holding on. I thought the shape was good, we defended the box really well. I think they've had one shot on target.
"Always happy to win, but against a good team with some good players, good manager, second best home record in the league. There were a lot of boxes ticked tonight."
Our midfielders continued their impressive goalscoring run on Friday evening, with Connell getting us off the mark and becoming the latest Reds player to open his account for the Club.
The winner came courtesy of Phillips, who with his driven strike made it five goals in six matches, a player seemingly benefitting from a tweak in system. The gaffer was happy for the pair, whilst acknowledging that it was a real team performance that got them over the line in Cambridgeshire.
"He scores a lot of goals in training, Luca," he discussed. "We don't want him to just sit in front of the back three and just protect. Some of his passes today were excellent and his technique is good. I was delighted for him.
"Obviously, two goals from outside the box. Adam, I think that's five in six now. Those two will get the headlines, but it was a proper team performance today."
Duff and his coaching team had to make numerous changes throughout the game due to injuries, with Tom Edwards having to come off to be replaced by Josh Benson.
However, Benson himself was forced to leave the field of play due to injury, with Robbie Cundy slotting into the backline in what was an ever-changing Reds defence throughout the affair. Our Head Coach was really pleased with the mentality the whole team showed to get over the line against Posh.
"One of the standouts for me, Robbie Cundy could have sulked when we put Josh Benson on ahead of him," he said. "The natural one would have been putting Robbie in for Tom (Edwards).
"He comes on when they're lumping the ball in the box and he heads everything out. I think there's three headers in the last couple of minutes. Robbie had three headers, Kitch (Liam Kitching) had a header, Luca took a kick in the head, and every single time the whole bench went up like we'd scored. That's all going on behind me, but that's real togetherness."