Bob Bell is the latest to quit Manor with the technical consultant leaving the team just a few months after he joined.
Just weeks after Manor announced an engine partnership with Mercedes, it emerged during the Mexican Grand Prix weekend that team principal John Booth and sporting director Graeme Lowdon are set to leave at the end of the season.
Former Renault and Mercedes technical boss Bell has joined the exodus, five months after he took up the job, but unlike Booth and Lowdon he left the Banbury-based outfit a week ago.
There are reports that Bell will re-join the Lotus team, which is expected to run as a Renault works squad next year.
Mercedes motorsport boss Toto Wolff has admitted that the current uncertainty at Manor is not good following a few months of stability.
"Manor means John Booth and John Booth means Manor, and Graeme was very instrumental in keeping the team alive last year," he said in Friday's FIA press conference.
"So seeing them go, from a personal standpoint and from the racing spirit, is obviously a blow."