Keane needs a break - O'Neill
Republic of Ireland boss Martin O'Neill believes burn-out could have caused Roy Keane to quit as Aston Villa assistant manager.
The former Manchester United midfielder left as Paul Lambert's number two on Friday, just 24 hours before their Barclays Premier League game at Burnley.
Keane is also O'Neill's assistant with Ireland and said he was struggling to juggle his duties for club and country.
And former Villa boss O'Neill believes Keane needs a break after doing both roles since July.
"He didn't have any holiday - he went straight from international duty with us in America to the job at Aston Villa and eventually those things catch up with you, one side of Christmas or the other," he told FAI TV.
"Roy being the perfectionist he is wanted to give everything to every single cause, but I think maybe a bit of family time now is perhaps something which is missing.
"We had a big discussion about the issue at the last international get-together. He was more concerned about having that full commitment to Villa and to ourselves.
"I said in the past and it's worth reiterating - I never had a problem with his commitment to the Republic of Ireland. Everything I was hoping he would bring to the table - commitment, enthusiasm, the strong desire we know he possesses - haven't been a problem.
"I am delighted the Republic of Ireland have been his first choice."
Keane replaced Ian Culverhouse in the summer, with Lambert's former assistant having left at the end of last season following an internal club investigation.
The Irishman departs with Villa just two points above the relegation zone, and with Lambert under increasing pressure from fans.
They are winless in their last eight games and head to Turf Moor without key defenders Ron Vlaar, Philippe Senderos and Nathan Baker, while Christian Benteke is still suspended and Fabian Delph is recovering from a dislocated shoulder.
Lambert admits they must turn their slide around, but continues to defend his side's form.
"We've got to find a solution," he said. "We've got to get ourselves out of that (relegation-fighting) mode.
"In the last two games (both draws) we have merited points. If you look at the table, it's that tight this year.
"Arsenal are five points ahead of us and Liverpool are a couple - it's massive clubs like that who are round about that kind of area.
"With the way the table is, one win gets you up a few places. I'm under no illusions about that. It's not a position everybody here is happy with, but we have to find a solution to get up the table.
He added: "This year you don't know what's going to happen. You can't predict what's going to happen.
"We have to find a solution to get this club out of that mode of being down and round about it."
Asked whether he was under pressure, Lambert said: "From myself, yes.
"Whatever happens or comes from the top... you only put pressure on yourself.
"It's not actually something I talk about. The chairman will decide that. He'll decide what he thinks. At the moment I'll do the best I possibly can and see what happens.
"The pressure is there. Don't think for one minute that (owner) Randy (Lerner) sits there and thinks it's all plain sailing. The pressure is always there."