The Sheffield Star reports that Robertson is close to agreeing a deal to become Stephen Glass’ second summer signing after agreeing a pre-contract with Celtic captain Scott Brown.
Robertson has made it known to his club Rotherham United that he won’t be signing a new deal and a move back to Scotland seems on the cards.
Known for playing full-back in the North East, the 27-year-old has largely operated in central defence since signing for Blackpool in 2015.
His form for the League One club saw Rotherham calling in 2018. Though they were relegated from the Championship in his first season, Robertson helped them achieve immediate promotion back to the second tier.
Injuries have curtailed his involvement over the past two seasons, including only 16 appearances this past campaign.