Steve Bruce has left his role as manager of newly promoted Premier League club Hull City.
The 55-year-old, who did not take training on Friday, had said earlier this summer he was uncertain of his future at Hull, who are up for sale.
A breakdown in his relationship with vice-chairman Ehab Allam contributed to his departure.
Bruce is odds-on favourite with some bookmakers to return to former club Sunderland and replace Allardyce.
Former Manchester United captain Bruce became Hull boss in 2012, and led them to promotion last season.
During his time at the KC Stadium, he led the team to two Premier League promotions, an FA Cup final and Europa League qualification.
He raised doubts about his position following the play-off final win over Sheffield Wednesday in May.
He suggested at the time he could leave the East Yorkshire outfit unless there were "certain assurances that we're all moving in the right direction".
|Steve Bruce's Hull record|
|Two promotions to the Premier League (2012-13, 2015-16)|
|FA Cup final (2014)|
|Europa League qualification (2014)|
In June he said it was "business as usual", but once again fuelled speculation about his future in July by stating any new owners of the club might want him replaced.
Earlier this week, Hull said they would put takeover talks on hold until September to "ensure stability during the transfer window".
Injuries have left the club with only 13 fit players, and they said they would look to strengthen the squad in the "coming weeks".
They open the Premier League season by hosting champions Leicester on Saturday, 13 August.
Bruce began his managerial career with brief spells at Sheffield United, Huddersfield Town, Wigan Athletic and Crystal Palace before a six-year stay at Birmingham City. He twice helped the Blues win promotion to the top flight before returning to Wigan in 2007.
Bruce was then brought in by Sunderland in 2009, before he was sacked two years later with the club in 16th position.