Black has left his position as number two at the Millers to do a similar role at Aston Villa, with the Premier League club announcing it this afternoon.
Halford's demise at Rotherham, where he has been told he has no future, began with a major training ground bust-up with Black in late September and the utility player was left out of Black's matchday squad in his only game as caretaker manager.
That led to Halford's first of many Twitter outbursts, slamming club "politics" and his position at the club only worsened as new boss Neil Redfearn deemed him surplus to requirements.
It is understood that Halford and Black's relationship was never repaired and less than an hour after Black's appointment at Villa Park was confirmed Halford posted a cryptic message, saying: "It's not what you know nowadays, it's who you know."It's not what you know, it's who you know nowadays.— Greg Halford (@GregHalford15) January 26, 2016
It is not the first time Halford has had cryptic but timely digs on the social media site.
In addition to his blast after his Burnley omission he has also suggested he was lied to about the position he would play when signing and that boss Redfearn had not told him he was surplus to requirements at the club.
Halford has not played for the Millers since a substitute appearance at Brighton in mid-September.
