Leeds assistant boss Steve Staunton has kept an eye on the Republic of Ireland defender, who has already won two full caps despite not yet appearing for Villa's first team.
He joined Southampton on loan in January and made one appearance, while he played 11 games for Wycombe last season.
His two international appearances for the Republic came against Ecuador and Bolivia last year.
Meanwhile, Parker has joined Darlington on a month's loan. The 20-year-old will provide cover for the suspended Alan White and Neil Austin and the injured Tim Ryan.
Parker spent last season on loan at Bradford and went on to make his Leeds debut at Macclesfield in August, but has not played since the 1-0 defeat to Southend in January.