Dawid Malan has stepped down as Middlesex captain, citing a poor County Championship Division Two season as the reason behind his decision.
Stuart Law's team could only win three of their 14 games in red-ball cricket and had to settle for an eighth-placed finish.
With hopes high they could challenge for promotion and return to the top flight for 2020, it proved an ultimately disappointing year.
"Middlesex played some fantastic cricket during the 2019 season, reaching the knock-out stages of both white-ball competitions - achievements of which we can be proud," Malan said.
"However, our form in the second division of the Championship was inconsistent and it was extremely disappointing to miss out on promotion.
"I have therefore decided to step down as captain to allow someone else the opportunity to work with the coaching staff to readjust and hopefully guide the team back towards the top of the first division.
"It has been an honour to captain Middlesex in recent seasons, and I would like to thank everyone associated with the club for their support."
Director of cricket Angus Fraser commented: "Dawid has thrown his heart and soul into the role of club captain for the past two years, and on behalf of Middlesex Cricket, I would like to thank him for that.
"He has also shown great pride and dignity in the way he has handled a difficult season and he leaves the role knowing he has given it all he can.
"As a batsman the captaincy seems to have got the best out of him and he has had an excellent season. He has been our best player in testing batting conditions.
"That things have not worked out as we hoped is disappointing for everyone involved and we must take the responsibility for that.
"Personally, I would like to thank Dawid for his commitment to the role and his desire to take the club forward.
"We must now turn our attention to finding a suitable replacement to take this great club forward."
Middlesex also confirmed Miguel Cummins had signed a new three-year deal with the club and Nathan Sowter had extended his stay at Lord's until the end of the 2021 season.
Ollie Rayner and Tom Barber will move on, though, despite the former taking 51 wickets in the 2016 County Championship Division One success.