Knox, 21, previously played under Simon Haworth at Clitheroe before moving to Colne in December 2017.
He said: “I’m delighted to be signing for Stalybridge and I’m looking forward to a new challenge in a different league, hopefully I can help the team get as many wins as possible.
“I can’t wait to get started.”
Ustabasi arrived at Bower Fold back in September and scored four goals in his first season, earning him the Fans Player of the Year award.
Haworth said: “Jon was sort of top of the retain list. He fits in to what we’re trying to do, we’re trying to play a bit more football and play with a bit more energy. I think Jon will suit that.
“Brad came to me in my first season at Clitheroe when he was only 16. He’s a very good footballer and scored some good goals for me.
“He can do a bit of everything but it’s very much about Brad getting his head down and working hard and realising that he can fulfil some of his potential.”