Herd has recovered from a hamstring injury.
But the 24-year-old utility man has not been in Paul Lambert's matchday squad since the turn of the year.
In a statement, Villa said: "The club can confirm that due to personal reasons Chris Herd will be unavailable for selection until further notice. There will be no further comment and we request that Chris's privacy be respected."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball