The 24-year-old is poised to leave Villa Park without ever making a first-team appearance, just one year after joining from Juventus for an initial £6.7m.
Barrenechea spent the whole of last season on loan at Valencia and had no shortage of suitors after an impressive campaign in Spain.
It is Benfica who are now expected to secure his signing after talks with Villa accelerated over the recent days.
Barrenechea’s arrival last summer coincided with the sale of Douglas Luiz to Juventus for £42.5m and was one of three separate deals done between the clubs, with Villa also signing Samuel Iling-Junior for an initial £11.8m. The sale of Luiz was critical to Villa complying with the Premier League’s profit and sustainability rules.
Boss Unai Emery kept a close eye on Barrenechea’s progress with Valencia and while acknowledging the Argentine’s talent, there were doubts over his chances of regular game time this season, due to the level of competition in Villa’s midfield.
The club replaced Luiz last summer with the club record £50m signing of Amadou Onana, while Boubacar Kamara, John McGinn and player of the season Youri Tielemans are all competing for central roles.
Barrenechea will become the latest senior player to leave this summer, after Kaine Kesler-Hayden having joined Coventry and Kosta Nedeljkovic returned to RB Leipzig on a season-long loan.
Teenage forward Zepiqueno Redmond is the only arrival so far, though Villa hope to complete the signing of goalkeeper Marco Bizot on Tuesday.