Clark Robertson in action for Rotherham at the New York Stadium.
Aberdeen face competition from Portsmouth to sign free agent Clark Robertson.
According to a report in the Daily Record, English League One side Pompey are keen on the out-of-contract Rotherham United defender.
Robertson came through the ranks at Pittodrie before moving to Blackpool in 2015. He is reaching the end of his three-year deal at Rotherham.
Dons manager Stephen Glass is keen to bring the 27-year-old back to his hometown team and Robertson is understood to have visited Cormack Park to meet the new Reds boss.
Clark Robertson in action for Aberdeen in 2015.
Robertson made 68 appearances for the Dons between 2009 and 2015.
Aberdeen have already signed Celtic captain Scott Brown, Motherwell skipper Declan Gallagher and Oldham goalkeeper Gary Woods on pre-contract deals, while striker Jay Emmanuel Thomas joined on a two-year deal after leaving Livingston earlier this week.
They have also been linked with St Mirren attacking midfielder Jamie McGrath and Hibernian midfielder Jackson Irvine.
Aberdeen face competition from Portsmouth for defender Clark Robertson
