It is understood the club will reluctantly listen to offers for the 23-year-old after the academy graduate intimated he saw his future elsewhere.
Manager Paolo Di Canio had wanted to extend Colback's contract but with only 12 months now remaining on it the Black Cats would rather sell him now than allow him to leave for free.
Colback has been with Sunderland since the age of 10 but found opportunities in midfield difficult to come by last season and he played a chunk of the campaign as an emergency left-back.
Di Canio had hoped to give Colback more of a run in his preferred position, especially with the likely departure of Lee Cattermole this summer, but the player feels he needs a new challenge.
Even if Cattermole does move on there is still plenty of competition in midfield as Di Canio's summer overhaul of the squad has seen him bring in Cabral from Basle.
The 24-year-old, who was available on a free transfer, claimed he turned down some Champions League clubs in order to be able to work with the charismatic Italian.
"I had a lot of offers and a lot of clubs were interested in me, including some who were in the Champions League," he said.
"But I think I wanted to choose a club where the coach was ambitious.
"I had two conversations with Di Canio and I got the sense that he wanted to achieve something here with the players he was looking to bring in.
"I wanted to come to Sunderland and play in the Premier League.
"I'd prefer to come to Sunderland than Arsenal, Everton or Tottenham where I might only be on the bench.
"I've got the chance to play regularly for a good club like Sunderland but most of all I chose Sunderland because of Di Canio.
"It's definitely been a dream of mine to play in the Premier League and now it's come true."
Cabral, like Colback in some respects, wanted a new challenge and opted not to stay with his Swiss club - where he had won five league titles, three domestic cups and played in the Champions League and Europa League.
"I had an offer to stay at Basle, which was a good one and I was happy at the club," he told the Sunderland Echo.
"But I felt like I had won everything there. It was a good note to leave the club on after winning the league again but it was the right decision to leave.
"I needed a change. I'd spent four years there and everyone was great with me but I wanted to progress in my career."