With United trailing to Kevin Smith's first-half strike, Ciftci fired home the equaliser in the 69th minute before setting up Ryan Gauld to put the visitors in front.
Mitch Megginson scored a wonderful late equaliser but Dutch-born Turkish youth international Ciftci soon hit an 89th-minute winner to give United a 3-2 second-round win.
McNamara said: "I'm delighted for Nadir, I thought he was excellent.
"I told him to get in behind them with his strength. I knew he would cause them problems.
"It was a good ball from (Paul) Paton and an excellent first touch and great finish. He was excellent for Gauldy's goal as well, good strength in their box and a good ball across.
"He is a fantastic talent, I think everyone can see that.
"It's down to myself and the staff to make sure we get the best out of him every time he plays and that he keeps improving.
"He is only 21 years old and you can see he's a real prospect."