Obertan left Old Trafford for the Toon last summer.
"Yes, I think it would have worked out at Manchester United," he told The Journal. "I don't know how long it would have taken.
"I didn't want to spend another two years learning and fighting for just a few minutes on the pitch here and there.
"I had to make a decision and it was very difficult but I needed to play, and here at Newcastle's it's a great opportunity."