Martin O’Neill surprisingly resigned as manager of Aston Villa on Monday, just five days before the start of the Premier League season.
Villa announced the decision on its website, but gave no reason for the sudden departure.
"I have enjoyed my time at Aston Villa immensely. It’s obviously a wrench to be leaving such a magnificent club," O’Neill was quoted as saying in the statement.
Villa aid reserve team manager Kevin MacDonald will take over the team on a temporary basis until a permanent replacement is found. Villa plays West Ham at home on Saturday in its Premier League opener.
"The club would like to thank Martin for the great work he has done at Aston Villa over the past four years," club chief executive Paul Faulkner said. "He has helped to establish the club in the upper echelons of the Premier League, has taken us to Wembley and we have also qualified for European competition for the past three seasons under his management."
Villa finished sixth last season for the third year in a row, and O’Neill has been widely credited for making the club a solid contender for the European spots.
However, the club has failed to break into the top four of the Premier League, and O’Neill has reportedly been at odds with American owner Randy Lerner over a perceived lack of financial backing needed to make the club a Champions League contender.
Last year, the club sold England midfielder Gareth Barry to Manchester City – which is also pursuing Villa’s James Milner this transfer window – but did not buy a high-profile replacement.
Lerner said in May that O’Neill had agreed to stay at the club after weeks of speculation that he might leave.