Birmingham City have sacked Wayne Rooney after just 15 games in charge.
Rooney was appointed at St Andrew's on October 11 on a three-and-a-half-year deal with the club sixth in the Championship following back-to-back wins under sacked manager John Eustace.
But Rooney has seen his team lose nine of the 15 matches they have played since he took over, leaving the club in 20th place in the Championship table.
Rooney released a statement in the wake of his sacking, which read: "I would like to thank Tom Wagner, Tom Brady and Garry Cook for the opportunity to manage Birmingham City FC and the support they all gave me during my short period with the club.
"Football is a results business - and I recognise they have not been at the level I wanted them to be. However, time is the most precious commodity a manager requires and I do not believe 13 weeks was sufficient to oversee the changes that were needed.
"Personally, it will take me some time to get over this setback. I have been involved in professional football, as either a player or manager, since I was 16. Now, I plan to take some time with my family as I prepare for the next opportunity in my journey as a manager.
"Finally, I wish Birmingham City FC and its owners my best wishes in the pursuit of their ambitions."
Birmingham suffered a 3-0 defeat at Leeds on New Year's Day, after which Rooney vowed to fight on as manager of the club.
"I'm a fighter and I get football fans' opinions," he said. "I have to draw on my career, my playing career wasn't always about success. I was in a relegation battle with Everton, I believe in myself."
Birmingham chief executive Garry Cook said "We are committed to doing what is necessary to bring success to St. Andrew's.
"Unfortunately, Wayne's time with us did not go as planned and we have decided to move in a different direction.
"The search for a successor begins with immediate effect and we will update supporters when we have further news."
The former England and Manchester United captain was the first managerial hire by new Birmingham owner Tom Wagner and his Knighthead Capital Management group, who bought the Championship club in August.
In his mission statement after taking over the club, Wagner spoke about implementing "the addition of exceptional leaders who are experienced in world-leading sporting businesses".
But results failed to fall Rooney's way - and after their 3-1 defeat to Stoke on Boxing Day, he questioned the "personal pride" of the Birmingham squad.
"The players in there are good enough. I believe that," he told Sky Sports. "They've shown me they can do it against big teams in this league.
"There's no excuse for putting in good performances then doing that today. It's unacceptable and personal pride has to come into it.
"Today I have questioned that because we were nowhere near good enough and not a team I want to put out."
"It's not an unexpected decision. The only surprise here is that it's happened so quickly. Wayne Rooney has only had 15 games in charge of Birmingham City and his was a landmark appointment by Tom Wagner, who had only bought the club in August, and this was his first appointment.
"He wanted Wayne Rooney to take Birmingham back to the top of the Championship and ultimately back into the Premier League.
"That's the ambitions that the new owners had but they felt they had to act now with results as poor as they have been.
"Birmingham have had some injuries as well but I wonder how big an impact some of their fans have had on this decision by Tom Wagner and his Knighthead Capital Management group.
"As Rooney walked off at Elland Road on Monday, a pretty substantial number of supporters chanted 'Rooney, it's time to go'. The fact that fans have turned against Rooney at this stage was pretty significant from the owners' perspective.
"Nevertheless, it's a big blow for them and it's a big blow for Rooney. He will feel he was building something, and of course with the transfer window only just opening - and I expect Birmingham to do business in this window with money to spend - he will have felt he needed more time to get his players in.
"The people I've spoken to at Birmingham City since they appointed Rooney made it clear to me that this was a very carefully thought-out decision to appoint him.
"It wasn't just about the football. They wanted a figurehead, they wanted a former England captain and they wanted England's former leading goalscorer to increase the commercial opportunities at Birmingham City as well as getting results on the pitch.
"They thought they were appointing a young manager who had always been popular and highly thought of by every group he's ever worked with.
"I got to know him well at Derby County when the club were in administration and had the points deduction. They were ultimately relegated but Derby made a real fight of staying in the Championship.
"The players and the staff couldn't speak highly enough of him and how he galvanised the group and how he led the club as a whole - not just the football operation.
"That's what Tom Wagner thought he was getting when he appointed Rooney - a huge personality and a huge name in football to try to drive the club forward into the top end of the Championship and ultimately the Premier League.
"Tom Brady is a bit of an investor in Birmingham City and it was a bit of a dream team. Brady the NFL superstar and Rooney the 'soccer' superstar together at Birmingham but it hasn't panned out. It's pretty much been an unmitigated disaster.
"It's not what Knighthead Capital expected. They wanted to build a squad for promotion but now they have to piece together a team that can stave off relegation."