Former England defender Sol Campbell has left League Two side Notts County by mutual consent after only one game.
Executive chairman Peter Trembling told the club website Campbell "could not adjust to the long-term nature of the project under way at Notts County".
The 35-year-old former Portsmouth, Arsenal and Tottenham player arrived as a free agent in August to team up with ex-England boss Sven-Goran Eriksson.
But his debut, a 2-1 loss at Morecambe on Saturday, was also his final match.
Campbell's footballing future is now uncertain.
He is highly unlikely to be allowed to join a Premier League club before the January transfer window unless he can prove he had a just sporting cause for quitting Meadow Lane.
"There's no point in having somebody who doesn't want to play here," Trembling told BBC Radio Nottingham.
Chairman puzzled by Campbell exit
"Sol, I think, has still got one eye on the 2010 World Cup squad.
"Maybe he just wants to ply his trade elsewhere. Maybe the decision he made when he signed here was made a little too quickly.
"I think Sol expected this to be Premier League tomorrow almost, which by definition is not going to happen.
"We are on a five-year project, we are in League Two at the moment, we were up at Morecambe on Saturday and I think the stark reality of that compared to where he used to play at - the Emirates and Anfield etc - perhaps brought it home."
Campbell agreed a five-year deal with Notts County after his contract with Portsmouth expired, earning a reported £40,000 a week.
It was the biggest coup pulled off by the Magpies following the takeover by Munto Finance and arrival of Eriksson as director of football.
But following Campbell's hasty departure and with the Football League yet to ratify Munto's takeover of the club, Trembling is keen to reassure fans that they have no reason to worry about the club's future.
"The investment project is on track; we have brought in a lot of new players and resources into the club but obviously this is a five-year project, not a five-week one," he stated.
Campbell, who has won 73 England caps, began his playing career at Tottenham before making a controversial move to bitter rivals Arsenal in 2001.
In five years with the Gunners, he won two Premier League titles and three FA Cups and was an integral member of the double-winning team of 2002 and the 'Invincible' squad that went through the entire 2003-04 league season unbeaten.
In February 2006, Campbell left Highbury at half-time after he was substituted in Arsenal's 3-2 defeat by West Ham.
He was at fault during the build-up of the Hammers' first two goals but it was stated at the time through his solicitor that the player only "needed some space".
He moved to Portsmouth in 2006, captaining them to FA Cup glory in 2008 and making 32 Premier League appearances last season, before his contract expired and he moved to Meadow Lane.
On agreeing to drop three divisions, Campbell revealed the prospect of working again with Eriksson had been a big draw and said he planned to play for the club for "at least three years".
"This club have got great ambition and I want to be a part of it," stated Campbell following his signing.
"Sven played a big role. He's a great man. He's managed all over the world and he knows his football, he's a proper guy.
"He has seen the future. It's a challenge but I think everyone connected to the club are prepared for that challenge. It's refreshing."
However, it appears the situation changed on Tuesday.
"He had taken part in training and then, rather bizarrely, was part of a photo shoot," revealed BBC Radio Nottingham's Colin Slater.
"Then he went for treatment for a little hamstring niggle, collected his boots and said goodbye to the few people who were around.
"I understand he had some further discussions with some of the top people at the club, including Peter Trembling, the executive chairman."
When the signing was announced, Campbell's decision to drop to League Two received a mixed reaction from his former bosses.
Tottenham boss Harry Redknapp, who managed Campbell at Portsmouth, revealed if he had been in charge of any other club than Tottenham he would have attempted to sign him.
"I think he is still a fantastic player," he said.
"In my opinion, he's still in the top six central defenders in the Premier League so for Notts County to get him in that division is incredible."
However, Arsene Wenger, who was Campbell's manager at Arsenal, expressed doubts about how he would handle dropping down a few divisions.
"Time will show if it is a good move for him," he added. "It depends what is in his mind, if it is purely a football move or if it is a long-term move that he wants to be involved afterwards as a coach.
"Maybe it can be a good decision if he wants to build something on the longer term. On the short term, he will suffer a bit because he is used to top-level football.
"When you move down, it is always difficult to cope mentally."
Watch Campbell's one and only game for Notts County
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