Stephen Warnock has moved closer to a possible reunion with former manager Martin O'Neill at Sunderland after being left out of the 18-man squad for the weekend friendly against Werder Bremen.
Warnock, 30, is thought to feel his days at Villa Park are numbered under new manager Paul Lambert and will be allowed to leave the club during the current transfer window, after entering the final year of his contract.
O'Neill has spent the summer monitoring developments with the former England left back he signed from Blackburn Rovers for £8 million in 2009, and would be interested in a reunion provided there is no excessive transfer fee involved.
Sunderland are even thought to be considering a 12-month loan with the option of a permanent deal on a free transfer in 2013.
Lambert is looking to raise further funds to sign Ipswich Town's Aaron Cresswell and Villa owner Randy Lerner is believed to be ready to take a significant loss on 30-year-old Warnock to remove him from the club's wage bill.
Warnock earns an estimated £45,000-a-week at Villa but was not asked to travel to Germany for the club's final preparation game ahead of the Premier League kick-off on August 18.
Lambert instead opted to use youngster Enda Stevens, and even used Fabian Delph out of position at left back, as Villa look to move the player on.
Championship clubs have asked about taking the defender on loan for 12 months, with Villa paying a significant percentage of his wages, but Lambert would prefer a permanent sale, with Villa hoping for a fee in the region of £1.5 million.
O'Neill is still looking for a left-back at Sunderland and remains a fan of Warnock, despite the troubles the defender has suffered at Villa Park over the last year.
Lambert appears eager to move on all the defensive old guard having sold James Collins to West Ham and telling Alan Hutton he can leave the club, despite having three years remaining on his contract.
Richard Dunne is another whose position remains uncertain, with Stoke City monitoring his situation, as manager Tony Pulis looks to fill the gaps left by the departures of Danny Collins and Jonathan Woodgate.