They dropped to 17th in the Championship after a 3-1 home loss to Blackburn, their fourth in a row.
However, the Canaries are now well on track for a play-off spot after five wins in their last seven games.
“We believed the entire time. “The question marks most likely came from outsiders,” Duffy added.
“It’s a really wonderful dressing room with great characters.
“We were disappointed [in November], and a few words were said at the appropriate time.” It was not pretty. We didn’t relish losing, but we always believed we had the right approach and that, with the talent we have in the squad, we could turn things around,” he told BBC Radio Norfolk.
A lot of people in the changing room understand that anything can happen in the Championship, so we constantly stick together.”
With three games remaining, David Wagner’s team, who won 1-0 against Preston on Saturday, needs a maximum of seven points to secure a top-six finish.
Their next two games come at home, against Bristol City and Swansea, where they have not lost since the Blackburn setback, before finishing the regular season away to Birmingham City.
“Not many teams will want to come to our place now with the way we’re playing,” said Republic of Ireland centre-back Duffy, who joined Carrow Road on a free transfer last summer.
“The manager was fantastic; he never got too high, never Too low and continued to rally us. We had a few guys return from injuries and just kept believing.
“I’ve always felt that with our squad, we should be at the top of the league, and now we’ve shown it on the pitch by letting our deeds speak for themselves.
“I’m delighted we turned it round and hopefully we can finish it off.”
