Chelsea have sacked manager Frank Lampard after 18 months in charge.
Former Chelsea midfielder Lampard, 42, leaves with the club ninth in the Premier League table after last week's defeat at Leicester City, having won once in their past five league matches.
His final game in charge was Sunday's 3-1 FA Cup fourth round win against Championship side Luton.
Former Paris St-Germain and Borussia Dortmund boss Thomas Tuchel is expected to succeed Lampard at Stamford Bridge.
Lampard was appointed on a three-year contract when he replaced Maurizio Sarri at Stamford Bridge in July 2019.
He guided them to fourth place and the FA Cup final in his first season in charge, and a 3-1 win against Leeds at the start of December put the club top of the Premier League.
However, the Blues have suffered five defeats in their past eight league games, as many as they had in their previous 23.
In a statement, Chelsea said: "This has been a very difficult decision, and not one that the owner and the board have taken lightly.
"We are grateful to Frank for what he has achieved in his time as head coach of the club. However, recent results and performances have not met the club's expectations, leaving the club mid-table without any clear path to sustained improvement.
"There can never be a good time to part ways with a club legend such as Frank, but after lengthy deliberation and consideration it was decided a change is needed now to give the club time to improve performances and results this season."
Owner Roman Abramovich said Lampard's status as an "important icon" of the club "remains undiminished" despite his dismissal.
"This was a very difficult decision for the club, not least because I have an excellent personal relationship with Frank and I have the utmost respect for him," said Abramovich.
"He is a man of great integrity and has the highest of work ethics. However, under current circumstances we believe it is best to change managers."