The winger will become a free agent next month with Derby and Crystal Palace among those interested in securing his signature.
Croft told the Eastern Daily Press: "It's sad because I have really enjoyed my three years playing at Norwich, although we've been struggling, especially for most of this season. I just feel it was time to move on.
"We had been in discussions before we were really in the relegation battle but then after we were relegated I had more discussions and I just felt it was time for me to move on and hopefully try and better myself.
"I would love to have stayed. I had no reason to want to leave but things didn't work out and regretfully I have to move on in my career. It's nothing to do with money - it's a football thing.
"If we'd stayed up I would have been talking to the gaffer and we would have been coming to an agreement right now to stay for another three or four years. That wasn't to be and at this point in my career I need to be playing at the highest level possible."