Sources: Robertson undergoes Portsmouth medical as Plymouth, Sunderland and Aberdeen beaten in race
Scottish defender Clark Robertson is undergoing a Portsmouth medical this afternoon as he completes a free transfer, Football Insider understands.
A source has told Football Insider Portsmouth have now agreed terms with Robertson and he will become their second summer signing if he passes a medical.
The deal could be completed in the next 24 hours.
Pompey have already added teenage left-back Liam Vincent from National League side Bromley.
Danny Cowley is looking to build a side capable of earning promotion from League One after taking over from Kenny Jackett in March.
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They finished in eighth-place last term, two points behind the play-off positions.
Robertson has experience of winning promotion from the division after playing 17 games in the curtailed 2019-20 campaign when Rotherham finished second on points-per-game.
He ended his three-year spell with the Millers with five goals and five assists in 69 games across all competitions.
Rotherham suffered relegation back to the third-tier last season as Robertson featured in 16 Championship games as he struggled with a foot injury.
Aberdeen were interested in taking him back to the club he began his career at.
Robertson played 68 games across all competitions for the Dons and was part of the side that won the Scottish League Cup in the 2013-14 campaign.