The 20-year-old injured his anterior cruciate ligament while training ahead of Sunday’s 2-1 win over Portsmouth and will be out of action for eight months.
The former Leeds United midfielder will be out of action until November as he recovers from the setback.
A statement on Villa's official website read: "Fabian Delph suffered a rupture of the anterior cruciate ligament [ACL] in his left knee in training on Saturday at Bodymoor Heath.
"Fabian will undergo ACL reconstruction at the appropriate time in the near future and it is expected that he will sidelined for a period of up to eight months.
"All Villa supporters will wish Fabian a full and as speedy as possible recovery."Delph joined Villa from Leeds in the summer but has not featured regularly for Martin O’Neill’s side, making just eight Premier League appearances.
Become a fan of Goal.com International on Facebook! Just click onto Facebook.com/Goal to join the beautiful game's leading fan community...