Roy Keane has resigned as Aston Villa assistant manager to concentrate fully on his role with the Republic of Ireland.
The 43-year-old moved to the Villa Park club in July, eight months on from being installed as assistant to Martin O'Neill with the Irish national team.
But just 12 league games into his first season alongside Paul Lambert, Keane has found the demands of balancing both roles too much to bear and leaves his position with the Midlands side with immediate effect.
"Ultimately, my roles with Villa and Ireland, and combining my commitment to these, has become too much," said Keane. "It isn't fair to either Villa or Ireland, so I've made this decision. I'd like to thank Paul for giving me a great opportunity to come to a brilliant football club.
"I've really enjoyed my experiences at Villa and I wish the management team, the players, the supporters and the club nothing but the best going forward."
Lambert added: "Roy came to me this morning and he informed me that, ultimately, the difficulty of combining both roles has prompted his decision, which I respect totally.
"In the brief period we have worked together he has been great in the role and I understand his reasons for leaving."
Though Ireland have played six matches this term, just two fixtures are scheduled before the end of the domestic season against Poland and Scotland as they continue their quest to qualify for the 2016 European Championships.
A club statement added: "Manager Paul Lambert will look to fill the position as soon as is practically possible and the club will support these efforts to secure the right appointment for the long-term."