Brown's return has been a big bonus for manager Paolo di Canio after last season's knee injury.
Brown said: "I did my medial ligament. There's been a few niggles in the meantime which set me back but it feels good to be back. I played one or two reserve games last season but I was never fully fit. I've always had injuries so I never doubted I could come back - it just took a little longer than expected.
"Mentally, I don't seem to struggle. I get my focus right and get it done.
"I never have a negative thought and that's one of the main things.
"It's no fun in the gym, it's the worst thing ever. It can be depressing but you have to be determined, get on with it and not moan."