Curtis, now 31, is playing for League Two club Northampton.
"There was a very different feel at United and I noticed that first of all when I went to Barnsley on loan, before I came to Blackburn," said Curtis.
"It was very cut throat at United. It was a very different environment.
"There was always a real pressure to perform. I suppose it filtered down from the first team.
"Don't get me wrong, it was fantastic at United but having played for 11 clubs I know more about what it's all about now and I suppose I look at it differently.
"Blackburn was a level in between United and Barnsley, but it was a real family club and compared to United it was quite homely."