The former Manchester United captain is said to have had a training ground bust-up with Aston Villa striker Gabriel Agbonlahor, in particular, which sped up his Villa exit.
Keane only moved to Villa Park at the start of the season to become Paul Lambert's no.2 but resigned late last month, citing the need to focus on the Republic of Ireland, where he is also assistant manager.
A source is reported to have told the Mail: "The atmosphere was horrible. It went downhill the moment Keane arrived. He p****d off all the big names he shouldn’t have p****d off and his relationship with the senior players slowly fell apart.
"There was so much gloom about the place every time he turned up. When he went there was just a feeling of euphoria and relief."
Aston Villa travel to West Brom at 3pm today for a crunch local Premier League derby.