Aston Villa have announced that assistant manager Roy Keane has left the club with immediate effect.
The 43-year-old had been splitting his time between acting as Paul Lambert's assistant at Villa Park and his role as Republic of Ireland boss Martin O'Neill's number two.
However, with Villa just two points clear of the Premier League drop zone, Keane has departed a day before they face Burnley in a vital encounter at Turf Moor.
Keane said: "Ultimately, my roles with Villa and Ireland, and combining my commitment to these, has become too much.
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.
"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 said on Friday morning: "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."
And Aston Villa CEO Tom Fox said: "We thank Roy for his time at the club and we wish him the best with Ireland.
"Our focus now will be on working with Paul to identify the right person to work alongside him and to help us continue on our journey to return the club to its rightful place in the Premier League."
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."
Former Manchester United midfielder Keane only joined Villa in July, after Lambert's previous backroom staff were sacked following an internal club investigation.
Number two Ian Culverhouse and head of football operations Gary Karsa departed at the end of last season after an inquiry into off-field issues.