Lee Bowyer is expected to become the next Birmingham City manager after leaving Charlton.
Bowyer announced his resignation as Charlton boss on Monday afternoon after three years in charge and is set to replace Aitor Karanka, who Sky Sports News has been told is no longer the Birmingham manager.
It is still unconfirmed whether Karanka has been sacked, resigned or has mutually parted ways with the Championship club - with senior executives at Birmingham due to discuss the managerial situation on Monday.
Bowyer took over Charlton as caretaker manager in March 2018 following the departure of Karl Robinson, and was permanently appointed six months later.
The 44-year guided the club to a third-place finish in his first full season in charge, beating Sunderland 2-1 in the play-off final at Wembley to win promotion to the Championship. However, Charlton only lasted one season in the second tier as they were relegated the following year.
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The club currently sit in eighth place in League One after winning 14 of their 35 matches this campaign.
Bowyer had signed a three-year contract in January last year which would have seen him stay at the Valley until the summer of 2023.
Johnnie Jackson will take charge of the first team for Tuesday's match against Bristol Rovers.
Bowyer said: "It was a difficult decision to leave. Everyone knows how I feel about the club. I could have gone before but I felt it was the right thing to do to stay and help the club through the tough times we've been through.
"We had some amazing times and some tough times. It has been emotional leaving. I'd like to thank all the players that I've worked with and the staff for the hours and hours of hard work that they did.
"I also want to thank the supporters. We wouldn't have had those great memories without them.
"The club is now in a place with a good owner that cares and wants to improve the place and I hope the club can continue to grow. It will always hold a special place in my heart."
Charlton owner Owner Thomas Sandgaard added: "I would like to thank Lee for everything he has done for Charlton.
"I have enjoyed working with him and wish him the best for his future. Our focus now is on finding the correct replacement to take this club forward."