The 24-year-old academy graduate is out of contract at Sunderland and the club are yet to successfully negotiate a new deal with the midfielder.
Gus Poyet completed the signing of Jordi Gomez on a free transfer from Wigan on Thursday and has reportedly made the initial advances to sign Jordan Mutch from Cardiff City.
Add to this the increasing speculation surrounding a move for Éver Banega and it appears the Uruguayan manager is resigned to losing Colback in the coming weeks.
Colback has previously been linked with moves to both Everton and his native Newcastle, but it was reported last week that West Ham were leading the race for the midfielder offering a huge £50,000-a-week contract.
Colback has made 135 appearances for the Black Cats since his debut in 2009 and his workrate, versatility and calm demeanour on the ball have resulted in the Tyneside born midfielder becoming a firm favourite with large pockets of the Sunderland fans.
It isn't yet known whether or not Colback features heavily in the future plans of Gus Poyet, or if Sunderland have the financial power to compete with the reported offer from West Ham, but with his best years still ahead of him; Colback is currently one of the biggest bargains available in the Premier League this summer.