Nottingham Forest's season has descended into farce after Alex McLeish left his post as manager at the City Ground only 40 days after replacing Sean O'Driscoll. McLeish's departure, which comes as no surprise after he was left deeply frustrated with the lack of activity in last month's transfer window, means that the al-Hasawi family, Forest's Kuwaiti owners, are now looking for their fourth manager since they took control of the club in July.

Rumours surfaced last Thursday night that McLeish had walked out after being bitterly upset with the club's refusal to sanction a deal for George Boyd, whose move from Peterborough collapsed because of an alleged eye defect. It was one of a number of signings that McLeish had hoped to make on a deadline day, only for none of the deals to come off. Forest's chairman, Fawaz al-Hasawi, insisted there was no truth in the rumours, and that he and McLeish "have a very good working relationship and it troubles me greatly that people think otherwise".

Although McLeish stayed on to take charge of Saturday's away game at Birmingham City, where he was returning for the first time since his highly controversial switch to Aston Villa in the summer of 2011, he did nothing to dampen the speculation about his position when he refused to answer questions about his future after the 2-1 defeat at St Andrew's. There was a sense of inevitability that he would soon be moving on.

That news arrived on Tuesday morning, when McLeish issued a statement, via the League Managers' Association, confirming that he had left Forest by mutual consent after seven games in charge that delivered one win, two draws and four defeats. "I am extremely saddened to be leaving after such a short period but even so it has been a privilege to be manager of such a fantastic football club and I want to thank the players, staff and fans for their support and wish Nottingham Forest the best of fortunes ahead.

"Both parties entered into the relationship in good faith. However, there was a difference in the understanding of the development strategy of the football club and it was felt by both parties that we should part company."

Nigel Adkins has been installed as the early favourite for the position, although it would be a brave man that takes the Forest job under the current owners and with so much turmoil behind the scenes. While it may not have come as a huge surprise when the al-Hasawi family sacked Steve Cotterill within 48 hours of completing their takeover, the decision to dismiss O'Driscoll, only hours after Forest had defeated Leeds United 4-2 to leave them only one point adrift of the play-off places, went down badly with many supporters.

Fawaz al-Hasawi, Forest's chairman, said on the clubs website: "I'm bitterly disappointed – as is Alex – that it has not worked out as we had hoped. I would like to put on record my thanks for his services and wish him every success in the future."