The 22-year-old is expected to play only his second game for the Black Cats since being sent off in August's humiliating League Cup defeat by Luton Town when the Wearsiders travel to West Ham United on Sunday.
Halford identified a lack of self-belief as the reason behind his failure to make an impact at the Madejski Stadium but feels he is starting to regain it after his recent performances for the Black Cats reserves.
"I lacked a bit of confidence when I came here after my experience with Reading but that is in the past," he told his new club's official website. "I feel I'm beginning to find my old form.
"I'm at a bigger club and there is more expectation but I'm feeling a lot better now and I want to be more positive. Confidence is a big thing, it's a major part of football and maybe I lacked a bit. But I feel much better and there is a lot more to come from me."