Middlesex head coach Richard Scott has left his position after nearly a decade in the role.
Scott was appointed during the summer of 2009 and his greatest moment came when Middlesex clinched the Specsavers County Championship title in 2016.
However, they were relegated last season and their hopes of regaining Division One status have been hit by three losses in their opening seven second-tier fixtures.
Assistant coach Richard Johnson, a former Middlesex seamer who played three Tests and 10 one-day internationals for England, will take charge for the remaining seven championship games.
Former New Zealand all-rounder Daniel Vettori will oversee Middlesex in the Vitality Blast, as he did for last season’s T20 campaign.
Middlesex’s managing director of cricket Angus Fraser said: “On behalf of Middlesex Cricket I would like to thank Richard for all that he has given the club as head coach during the past 10 years; he has been a loyal, hard-working, committed and high-quality coach.
“As with every coach in professional sport we have shared highs and lows, but to play a leading role in a side winning the County Championship is a triumph very few coaches can claim.”